There were only three cases we can trace with these types of airplanes where the Russians filed a flight plan. There was one not too long ago where they transited two Blackjack bombers from Russia to Venezuela for an exercise, which was publicized at the time. There was a flight near Iceland by the Russians. And the third one where there was a flight plan was off the coast of Alaska, if I'm not mistaken.
These are the only three that are known, and that's researching through international air traffic control agencies, Eurocontrol and others. If you look through the database, there were only three confirmed flight plans that were submitted.