zp_bridges .bsp's are lightmapped while zp_bridges_fixed .bsp's are fullbright like pw_bridges_big
The .rmf files are located in maps/mapsrc and two .wad's are located at the root of the zip. I can not find the last missing .wad meaning some textures will be missing the later versions of the map. This does not affect the included .bsp's, only the .rmf's if you decide to compile them yourself. Just replace the missing textures with something else and you won't have a problem.