OK, so I've come to a conclusion, that my fresh install of game (it's original, so it's not a fault of cracked software) does NOT have any .bed files in its "music" folder, so the files from "data.bfs" must overwrite the files from the mod each time at launch, which sucks.
BUUUUUUT...
I came with a workaround. You have to unpack "data.bfs" and "streamed.bfs" files with BFS Unpacker for FOUC, then rename "filesystem" to "filesystem_old" (it could be any different name, to be honest), so the game won't take this file into consideration at launch. Just unpack mod on top of it and everything works like a charm :D
Maybe versions from different countries have different file placement and/or are packed in different ways? Dunno ¯\_(ツ)_/¯ But if somebody has/will have the same problem, try this. Here's the link to BFS Unpacker that I've used (use BFS3pack_smart_gui): Sendspace.com
R0ckwe11
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