If you have the orginal model/map sources (3ds/blender etc) it's quite possible to import it as a map mesh.There are even tools provided by valve to do Google Sketchup to Hammer (the mapping tool for source engine)
Long time no post/talk, some people might remember my name, some may not. I have always liked APB and have always figured it could be redone in Garry's Mod. So far I have come up with this. The server as is, is playable, but because I am unsure if advertising is allowed or not you can find that information in the video instead of me posting it here. The hardest part will be adding vehicles, but it can be done.