I would also like to emphasize the importance of this option. It is actually not only for urban plans, but also for regular ones. An example is the attic on the second floor. On all the above floor there is not possibility to automatically show the attic, hence you must draw it with lines. Off course when changes come, you must manually update the lines in all the above stories.
A simple option but it can really help on reducing error and time to change information.
The BIMster @ AllesWirdGut
Currently: Archicad 26
User since Archicad 6.5 (2001)