From all that I have read, which is limited, it is my understanding that the Catholic Church in Russia ministers to those catholics who came into the country at different periods. Admittedly, this is not a subject I have researched very extensively.
I suspect that if you spoke with any Maronite or Melkite priest or hierarch who felt he could be completely candid (and maybe they couldn't), they would tell you the same thing.
Indeed that response was given to me last month ;-D. The bishop affirmed to my pastor that the Maronites do not 'evangelize', especially amongst other catholics. Which of course brings us back to the topic at hand. IF the Catholic Church does not evangelize in Russia but Orthodox christians wish to join the Catholic Church, why would the Orthodox Church have a problem with that? It's a personal freedom to choose one's religion, is it not? Does the Russian Orthodox Church have such power over the state to prevent the establishment of other christian churches in Russia?
I would question the premise that those churches loyal to the Pope -- Eastern or Roman rite -- don't evangelize and compete with the Orthodox Church in Eastern Europe, but rather just sit in their churches waiting for folks to show up. But assuming that this is exactly what they do, the Orthodox Church of course wouldn't have any problem with people choosing to join the Romans.
But the whole point to the Unia was that it was a tool to bring Orthodox Christians under the jurisdiction of the Pope by creating parallel churches that looked exactly like the Orthodox churches, except that they were under different bishops -- ones loyal to the Pope. This, needless to say, created a lot of hostility that exists to this day. Back in the "bad old days," as your own #72 itself points out, the Unia was clearly also a tool by which Rome intended to gradually change the practices and beliefs of the Eastern churches under its jurisdiction by Latinizing them.
The large exodus of American Uniates from the Catholic church back into Orthodoxy here in America in the late 19th century was spurred in no small part due to these already heavily Latinized Eastern Europeans being pushed just too far in that direction by the Irish hierarchy here in America with the help of Polish clergy. The Irish bishops here in the US had the misfortune of pushing the wrong guy: a widowed Carpatho-Russian priest named Alexis Toth (now considered a saint by the Orthodox Church in America) who just happened to be a professor of canon law and knew his rights under the terms of the Unia, which he quoted verbatim to the Roman bishop of Minneapolis in their now legendary meeting.
A couple hundred thousand former Uniates ended up coming under the jurisdiction of the Russian Orthodox Church here in the US (back when the Russians had sole jurisdiction here in the Americas.) Their path of undoing their Latinization has been a long but exciting one. I daresay that this experience played no small part in Rome's change of heart at Vatican II regarding how they would treat their Eastern Rites.
Within the last few days, incidentally, I posed a hypothetical corollary that the Orthodox could have carried out in places like Poland by creating an "Orthodox Latin Rite", and interestingly enough, no-one responded.
"It's a personal freedom to choose one's religion, is it not?"
Yes it is. But again, the point isn't that the Romans and their Eastern Rites shouldn't have the right to proselytize, it is that Rome can't have it both ways: it can't pursue both a competing parallel church strategy and a reunion strategy, and expect the Orthodox to be tolerate the former and be enthusiastic about the latter.
"Does the Russian Orthodox Church have such power over the state to prevent the establishment of other christian churches in Russia?"
Well, that remains to be seen as time goes by, but it does seem clear that President Putin is commited to helping the Russian Orthodox Church regain its former stature and place of honor within Russia. I think he understands that as far as Russia goes, if his country is to be a Christian country, its path to this is via its own Orthodox heritage.