Chriss, sometimes you surprise me. Have not you lived sufficiently long in the E.Europe to discover that most stories of the "not permitted" variety is a bunch of US propaganda?
The Catholic church in Poland could operate religious, political and educational institutions, including a liberal arts college (Catholic U of Lublin) which I believe even received some public subsidies. The Catholics also had their own press and a "parliamentary club" (not exactly a party) at the national assembly called Sejm. In fact, there were four political parties represented in the assembly - two more than in the US! However, the Polish United Workers' Party (not a "communist" party by name or even its own programme - they were a "socialist" party while communism was officially a not-yet -achieved stage of development) was guaranteed the majority of the votes.
The same was true for other religions (mostly Protestant) except for the parliamentary representation - but non-catholics represent only about 5% of the Polish society. Interestingly, many Jews became Catholic after WWII.
Wojtek