If you won't mind a bit earlier period: Volhynian Czechs, descendants of etnic Czechs who settled in the Ukraine during 1860s - 1870s, were allowed to repatriate back to Czechoslovakia, as a result of negotiation between Soviet and Czechoslovak government. Some did return in 1945, the largest wave was in 1947. About 35 thousand people returned.

Book about Volhynian Czechs: Jaroslav Vaculík, Dějiny volyňských Čechů 1868 - 1948, three volumes, year 2000.