There's problem (bug) in UBC-0.8-beta49.
UBC should run as late as possible (as it selected in config by default). But with Realistic Terrain Generation (in RTG world types) this mod runs before RTG.
I noticed that, when I found desert village with sandstone and UBC cobblestone variants. (Without UBC this village in RTG world with the same seed generates correctly - only with sandstone blocks). And I also reproduced this bug in another world.
All information and screenshot: here (in last two posts)