Currently, the compiler tools search for the "quake2" directory, which is why the bsp pack has a really bizarre directory structure. Also, the tools use .wal files. Paintball2 has mostly .jpg textures by default. I don't know that you'd want to clutter up your paintball2 texture directory with .wal files and rename the folder to quake2, but I guess if you did that, it should be possible.