In addition to what's already been mentioned, you may want to check Loose Alliances as well- the Atlantean Foundation has some ongoing operations in Eastern Europe, (particularly Ukraine) and there might be a couple other groups. You might also want to check
Shadowhelix.de, as long as you don't mind pumping some things through BabelFish. (Unless you already speak and read German.) Their articles seem to have some additional information that North American books and wiki do not.
But if all else fails, you may have to make some things up- There's hope that the upcoming Sixth World Almanac may cover Eastern Europe, but no way to confirm it yet. I'm currently planning a game which will be set in Ukraine, and am already leaning toward writing my own short supplement- just to explain what else has happened in the last 30-60 years and how the country has reorganised itself after the wars/occupation, provide some detail on the multitude of local crime syndicates, and stats for some of the [predominantly Russian] hardware that players will be encountering regularly.
If anything, it's an interesting corner of the world with a lot of good gameplay opportunities. By the sound of things, the few countries in the region that are not at war or still recovering from wars are much less in favour of NEEC membership than countries in the west. The scant information in SoE hints that Greece, Ukraine, and Western Turkey are working together to to form their own little Federation, and the Megacoprs are not particularly happy about it.