There have also been "discreet" instances of inter-communion between Orthodox and Episcopalians, and Orthodox and Lutherans, and Orthodox and Anglicans, and doubtless other interesting combinations.
However, for an Eastern Orthodox to take communion in a non-Eastern Orthodox church, is apostasy and is a grievous sin. Much better to die IN communion WITHOUT communion, than to die OUT of communion WITH "communion." For then you die outside the Church, which is the Body of Christ. This issue very often came up back in Arianism's heyday.
It is also completely not possible for an Eastern Orthodox priest to give communion to an Oriental Orthodox, or a Roman Catholic, or a Lutheran, or an Anglican, although it certainly happens. Many other "impossible" things do happen from time to time, but private unbelief doesn't erase the dogma, and private conduct doesn't alter the rule.
"Greco-Russian" is how the Eastern Orthodox Church was distinguished from other faith-confessions, back in the day. It just means the faith of the Greek Orthodox and the Russian Orthodox, which includes all the other Chalcedonian Orthodox. The modern distinction between "Eastern" Orthodox and "Oriental" Orthodox was very recently promoted and I read some old fuddy-duddy books. Even the distinction between "Roman Catholic" and "Eastern Orthodox" (whether Chalcedonian or anti-Chalcedonian) is of very recent vintage, comparatively. "Greek Catholic" used to mean "Greek Orthodox," etc., etc. So I was speaking in a slightly antique fashion, for no particular reason.