I've heard 5 min expoxy works. I'd really like to know as well, as I have a few collecting dust that I'd really like to work on. Regular type glues (wood/Elmers/etc) don't work well, or fall apart due to the porous nature of the plaster the walls and such are cast in.
Let me know how the 5 minute epoxy works. I've got an upcoming "Urban Warfare" campaign on another forum that needs a building or two.