You're going to have some problems importing into city engine, mainly due to the overlapping splines. You could try setting the anti-overlap check in RPGCMG to maximum, and/or create a sort of giant compound path from all the buildings,bucket fill the largest negative space and use the resultant fill as a shape to simplify things a bit.

I should be coming up with a more memory-efficient version of the program in the next couple of days to address all the crashes people seem to be experiencing...