Maya Binary Model (.mb)
Overview
This filetype is not directly useable by idTech4 games. However, it can be interpreted by the engine when converting models and animations into MD5 formats using the exportmodels console command.
Sources where more detailed information on this format can be gathered are listed below.
MayaImport
MayaImport its an utility used by idSoftware for importing meshes made in Maya in to the game, while no source ports ships this this .dll you can use modern day tools to achieve the same goal.