There is a database which links the calling number to an address for 911 calls. These days with cellphones, cable, and VoIP telephone services it's not quite so simple as just using the address where a line is installed.
My guess is that the 911 center is receiving calls from phone numbers which have these addresses listed incorrectly on the database.
I'm not sure of the details on how to get this checked or corrected, but you might like to post over on Telecom Digest (newsgroup comp.dcom.telecom). I know for sure there will some folk in there who could go into much more detail.
