So far I'm not sure this format can be decompiled like the others. Need to do more research and reverse engineering.
C# library for parsing and reading BSP (Binary Space Partition) structures in Quake-based game engines
The classes in this project exist to parse and store BSP structure information from various formats from many Quake engine forks.
Eventually the BSP Importer for Unity3D and the BSP Decompiler projects will both use this library.