Seems to me that some system could be put in place whereby outgoing cell-phone calls from a pinpointed location (within the rubble of a destroyed building) would be allowed to go through but other calls — particularly non-911 calls — would be blocked for a specified period of time during an emergency.

I'm sure it would be a lot of trouble for such a system to be implemented... but changes are already being made that were too much trouble to bother with before September 11th.