The question of the existence of the Holy Mysteries among the Roman Catholics is, in the Russian Church, a moot point. It appears that for the last 500 years the Russian Church has accepted all Roman Catholic Mysteries (Baptism Eucharist, Priesthood) as authentic, per se and not per economia at the point of reception into Orthodoxy. This may not be the teaching of the Greek Church and I daresay it is not the teaching of all of the Russian Church (for example the Russian Orthodox Church Abroad) but it is a teaching nonetheless.
In the early church, one finds two strands.
1) On the one hand, there is St. Cyprian and the Apostolic canons (the former very clear that rebaptism is necessary because the lines of the Church are easy to find and outside of those lines there are no sacraments or salvation; and the latter very clear that all heretics need to be baptized when entering the Church).
2) On the other hand, there is I Nicea 8, Laodicea 7, I Constantinople 7, Trullo 95, St. Basil 1, all of which allow for reception of different groups in different ways, while never fully explaining what that means to ecclesiological theories.
The two "strands" allow for three basic types of reception. Fr. George Dragas summarizes it this way:
According to these canons there are three ways of receiving heterodox into the Church: a) by re-baptism (actually, baptism), when the celebration of heterodox baptism is considered deficient or invalid either on account of deficient faith and/or practice, b) by Chrismation and signing of an appropriate Libellus of recantation of the particular heresy that the converts previously held, and c) by simply signing an appropriate Libellus or Confession of faith, whereby the errors of heterodoxy of the person received are properly denounced and the Orthodox faith is fully embraced.
Dragas, George D. "The manner of reception of Roman Catholic converts into the Orthodox Church with special reference to the decisions of the Synods of 1484 (Constantinople), 1755 (Constantinople) and 1667 (Moscow)." Greek Orthodox Theological Review 44, no. 1-4 (March 1, 1999): 235.
Since all three means of reception have been promulgated by Oecumenical Councils, it is always up to the Bishops and Synods of the day to decide which means of recption to emphasize and how to apply the tradition in the current age.
In his article, Fr. George argues that the Church decided to (re)baptize Roman Catholics starting as early as 1193. Many Byzantine and Latin sources confirm this. This also appears to be the practice employed in Russia at the time as well. Some sources list theological and liturgical reasons for rebaptism (e.g. sprinkling is unacceptable), but they also mention Rome's proselytizing actions in traditionally Orthodox lands, and, of course, the Fourth Crusade.
However, at the Great Synod of Constantinople in 1484, all of the Eastern Patriarchs agreed that reception of Roman Catholics should be by Chrismation and signing of a Libellus. The Synod published a service to that effect, in which the priest asks the person many doctrinal questions, performs a penitential chrismation, and then the person signs a Libellus.
What did this mean theologically, liturgically, or ecclesiologically? Different people interpret it different ways. While the Great Synod of Constantinople in 1484 allows for reception by chrismation and signing of Libellus, it also explicitly states that the Latins are heretics and it makes no attempt to explain if the former Latin Baptism was valid or invalid.
For the most part, it seems Orthodox Christians of all kinds adopted this practice and understood it as "economy" -- not much further explanation, nor much discussion of "invalid" or "valid," and no mention of "valorizing" previously empty forms. Things progress along these lines until the Synod of Constantinople in 1722. Fr. George summarizes the history this way:
in 1575 Patriarch Ieremias II (1572-1594) explicitly criticized in his correspondence with the Lutheran theologians of Tübingen the Baptism of single immersion or Baptism by sprinkling, but did not pronounce it as invalid. But in 1715 Dositheos of Jerusalem stated that the Latins who are not baptized by triple immersion run the risk of being regarded as un-baptized. In 1708 Patriarch Kyprianos (1708-1709) regards the Baptism of the Latins valid by economy. In 1718, Patriarch Jeremías III (1716-1726) was asked by the Russian Czar Peter the Great about the baptism of the Westerners. In his letter to the Czar dated 31 Aug. 1718 the Patriarch referred to a synodical decision by his predecessor Kyprianos (1708-1709, which stipulated that Chrismation should be the means for receiving Lutherans and Calvinists into Orthodoxy after their renunciation of their errors. As the time went by, however, and conditions changed in the life and relations of the Churches in East and West, liturgical practice also changed. Western aggression in East called for a new policy. In 1722 a Synod in Constantinople, in which Athanasios of Antioch (+1724) and Chrysanthos of Jerusalem (1707-1731) participated, decided for the rebaptism of the Latins as retaliation for the schism that the Latin missionaries caused in Syria.
The Horos of the Synod of Constantinople in 1755 is very clear, very Cyprianic in ecclesiology, and emphatic that Latin Baptism is totally empty, being mere "useless waters." Over the next 200 years, this way of thinking was repeated by many in the ancient Patriarchates, from monks to Patriarchs, but it was not universally accepted. As Fr. George shows, there were many exceptions in the 18th and 19th century. However, St. Nikodemos, along with all of the Kolyvades, were firm believers in the Cyprianic view espoused by the Synod of Constantinople in 1755, so the Pedalion
(ca. 1800) makes it seem like (re)baptism of Latins is the only proper tradition of the Church. Thus, there are still many in the Greek speaking churches that hold to this view.
As for the Russian practice, it too punished the Latins for proselytizing at various points. For example, in 1620, a major Synod decreed that (re)baptism was necessary for all Latins and all Greek Catholics. But, not long thereafter, Peter Moghila published his famous Trebnik
(1646), which called for reception by Chrismation, and several Synods of Moscow allowed for reception by Chrismation only. As far as I understand it, that's been the practice of the Russian Church ever since.
Now, what this all means theologically, especially for ecclesiology, is another matter. As I wrote above, the early sources, the Byzantine canonists, and the ancient Patriarchates, do little more than speak of "oikonomia." The Pedalion
explains reception by some means other than Baptism this way:
[T]he two ecumenical councils employed economy and accepted the baptism of Arians and Macedonians and of others, but refused to recognize that of the Eunomians and of still others. This is because in the time especially of the Second Council the Arians and Macedonians were at the height of their influence, and were not only very numerous but also very powerful (...) Therefore, both in order to attract them to Orthodoxy and correct them the easier and also in order to avoid the risk of infuriating them still more against the Church and the Christians and aggravating the evil, those divine fathers thus managed the matter economically and condescended to accept their baptism.
In other words, it is "oikonomia" and it is employed because it (1) makes it easier for the heterodox to convert; and (2) it is more irenic, not producing ill will in the minds of others against the Church.
Again, no mention of "validity" or "invalidity" or "valorizing." In fact, Fr. George Metalinos, former Dean and current Professor at the School of Theology of the University of Athens, specifically rejects the idea that the Church teaches that Chrismation corrects or valorizes or supplements or makes whole a non-Orthodox Baptism, since this is not found in any early Fathers or Synods.
However, there are many later Russian sources that teach otherwise, starting in the early 19th century, as far as I've seen. Andrei V. Psarev published an article on this topic, and the earliest source he quoted with the full "valorizing" teaching was Aleksei Stepanovich Khomiakov (1804-1860), who wrote:
All Sacraments are completed only in the bosom of the true Church, and it matters not whether they are completed [...] in one form or another. Reconciliation renovates the Sacraments or completes them, giving a full and Orthodox meaning to the rite that before was either insufficient or heterodox, and the repetition of the preceding Sacraments is virtually contained in the rite or fact of reconciliation. Therefore the visible repetition of Baptism or Confirmation, though unnecessary, cannot be considered as erroneous, and establishes only a ritual difference without any difference of opinion. You will understand my meaning more clearly still by a comparison with another fact in ecclesiastical history. The Church considers Marriage as a Sacrament, and yet admits married heathens into her community without re-marrying them. The conversion itself gives the sacramental quality to the preceding union without any repetition of the rite. This you must admit, unless you admit an impossibility, viz., that the Sacrament of Marriage was by itself complete in the lawful union of the heathen couple.
Quoted in: Psarev, Andrei V. "The 19th canonical answer of Timothy of Alexandria: on the history of sacramental oikonomia." St Vladimir's Theological Quarterly 51, no. 2-3 (January 1, 2007): 297-320.
NB: Even Khomiakov starts his explanation with an insistence on Cyprianic ecclesiology. That's partly why Psarev concludes his article in SVTQ
My research leads me to the following conclusions: although in the practical aspect of reception the Church rather follows Augustine's understanding than that of Cyprian, nonetheless Cyprian's ecclesiology, that there are no mysteries outside the Church, was never refuted by the Orthodox Church. The attempt to reconcile this ecclesiology with existing grades of reception into the Church, as expressed by sacramental oikonomia, was only partially attended to by the Church Fathers (St Basil the Great, Blasteres, St Nikodemus). I was not able to find evidence that any of the Fathers who composed the canons held the position that in the reception of baptism performed outside the Orthodox Church, only the external form was accepted, and that this form might be filled by grace at the moment of reception...Nevertheless this theory enjoyed a place within the main body of Church law of the Russian and Romanian Orthodox Churches and was shared by noted authorities of Orthodox theology.