Well, the partisans in partisan commander are polish, they use some lines that make it pretty obvious in polish version of the game and to lesser extend in english version.
I am aware of Anya in the campaign. But that is where she remained. I have to confess I was unaware the Partisan Commander and its acolytes were meant to be Polish. Can you expand on that one for me, please? I always assumed the partisans in automatch were meant to be Soviet citizens.
I don't know about other language versions. They also use same lines and models as partisans in campaign and these are outright said to be polish Home Army soldiers. That's why soviets kill them at the end.
Other than the Ostruppen, and Anya, I freely confess I was unaware of any other East European involvement in the main game.