I wanted to import brushwork from a different engine to UDK, and as part of the research process I tried exporting a simple BSP-only level to T3D and importing it back. And guess what? It doesn't work. UnrealEd does create the brushes with the appropriate vertices etc., but the CSG operations are not carried out and all the brushes disappear upon trying to select anything in the world. The console logs complain about missing brush models. Any ideas?

EDIT: My bad, it was enough to rebuild level geometry (Build -> Geometry (Visible Levels)).