The Catholic Church rejects the idea that Grace is the indwelling of the Holy Spirit only and not the other Three persons of the Trinity.
I don't think I've ever heard or read anything to the contrary. I thought that's what we all believe.Actually, Roman Catholics and some others hold that Grace is either created (gratia creata accidentalis) or uncreated (gratia increata substantialis), and the latter is identified as the indwelling of the Holy Spirit.
From the Orthodox point of view, the Uncreated Divine Energies emanate from all Three Persons of the Holy Trinity and they are not identified as being the Person of the Holy Spirit.
Perhaps I have misunderstood the Catholic Encyclopedia, but it seems to suggest this:
"The crowning point of justification is found in the personal indwelling of the Holy Spirit. It is the perfection and the supreme adornment of the justified soul. Adequately considered, the personal indwelling of the Holy Spirit consists of a twofold grace, the created accidental grace (gratia creata accidentalis) and the uncreated substantial grace (gratia increata substantialis). The former is the basis and the indispensable assumption for the latter; for where God Himself erects His throne, there must be found a fitting and becoming adornment. The indwelling of the Holy Spirit in the soul must not be confounded with God's presence in all created things, by virtue of the Divine attribute of Omnipresence. The personal indwelling of the Holy Ghost in the soul rests so securely upon the teaching of Holy Writ and of the Fathers that to deny it would constitute a grave error. In fact, St. Paul (Romans 5:5) says: "The charity of God is poured forth in our hearts, by the Holy Ghost, who is given to us". In this passage the Apostle distinguishes clearly between the accidental grace of theological charity and the Person of the Giver. From this it follows that the Holy Spirit has been given to us, and dwells within us (Romans 8:11), so that we really become temples of the Holy Ghost (1 Corinthians 3:16 sq.; 6:19). Among all the Fathers of the Church (excepting, perhaps, St. Augustine) it is the Greeks who are more especially noteworthy for their rapturous utterances touching the infusion of the Holy Ghost. Note the expressions: "The replenishing of the soul with balsamic odours", "a glow permeating the soul", "a gilding and refining of the soul". Against the Pneumatomachians they strive to prove the real Divinity of the Holy Spirit from His indwelling, maintaining that only God can establish Himself in the soul; surely no creature can inhabit any other creatures. But clear and undeniable as the fact of the indwelling is, equally difficult and perplexing is it in degree to explain the method and manner (modus) of this indwelling."
First I just wanted to show that sanctifying grace is a participation in the Divine Nature:
" The climax of the presentation of the nature of sanctifying grace is found in its character as a participation in the Divine nature, which in a measure indicates its specific difference. To this undeniable fact of the supernatural participation in the Divine nature is our attention directed not only by the express words of Holy Writ: ut efficiamini divinae consortes naturae (2 Peter 1:4), but also by the Biblical concept of "the issue and birth from God", since the begotten must receive of the nature of the progenitor, though in this case it only holds in an accidental and analogical sense. Since this same idea has been found in the writings of the Fathers, and is incorporated in the liturgy of the Mass, to dispute or reject it would be nothing short of temerity. It is difficult to excogitate a manner (modus) in which this participation of the Divine nature is effected. Two extremes must be avoided, so that the truth will be found." - New Advent (Catholic Encyclopedia)
And as for your question about whether or not sanctifying grace is the indwelling of the Holy Spirit:
"From this it follows that the grace must be as distinct from the Holy Ghost as the gift from the giver and the seed from the sower; consequently the Holy Spirit is our holiness, not by the holiness by which He Himself is holy, but by that holiness by which He makes us holy. He is not, therefore, the causa formalis, but merely the causa efficiens, of our holiness." -New Advent (Catholic Encyclopedia)
This will lead to further discussion because of the word distinct found above. I am sure you picked up on this as soon as you read it.
All quotes from the New Advent Catholic Encyclopedia Article on Sanctifying Grace.