Great thing, GrumblingHive! I wish there would be a Windows Version and a script for PS...
Loading your test file into Illustrator(CS4) was no problem. I saved it as *.dxf and imported it into City Engine. The streets are imported correctly (I have to play with the scale), but the shapes of the houses are not. Let's see if we could solve this.
Is there any chance of a script, or most appreciated a test file with houses of combined house shapes if the overlap?