For Czechoslovakia: I don't know how typical this is, but in the Most District
https://en.wikipedia.org/wiki/Most_District where "Settlers--mostly young and unattached-—came to work in Most's factories and mines, and to acquire German property...Settlers had little connection to the natural and built environment of Most, or to each other. This made them particularly amenable to the productivist identity advanced by the Settlement Office and leading Communist politicians. Indeed, the Most district gave Communists a commanding 58 percent of the vote in the 1946 election..."
https://books.google.com/books?id=o-EZDgAAQBAJ&pg=PT135
I don't know if it would be possible to give any figures for Poland because the 1947 election figures were thoroughly falsified by the Communists.