@Screamer It is shared between Russia and the Central Powers. This is the fate of all contested original Russian territories, regardless of which powers are present in them at the time (if Russia has no units present, one Russian infantry is added).
If you happen to have the Avalon Hill version of the game, be sure to check out the Renegade version of the rulebook, found on the Renegade Axis & Allies resource page. It was revised to include all of the material from the official FAQ.