Agreed, it wasn't the GPS's fault here. They unknwoingly registered the wrong address.
There are also downsides to a central dispatching system. The major one I see is that in our county, which has an automatic response area (i.e. mutual aid is automatic, there is not need to call for mutual aid. The computer finds cloest avalaible units to the incident location and dispatches them regardless of which district things happen in. We are mutual aided to a neighboring suburb all the time since our station is clower to the boarder than theirs are) and a population of over 1.7 million, is that things take forever to dispatch. Granted with your system they also take forever to dispatch, but we only have one main dispatch channel so if a lot of calls come in at once, we have the dispatchers to handle to calls, but we might be waiting 5 minutes for the "stacked" dispatches to be put out on the dispatch channel.
Furthermore, with that many stations on one frequency, it's easy to hit the wrong buttons and open up the wrong station's PA system or not open one up at all! Finally its hard to keep track of who staffs what and what is in service.
One of the suburbs has 2 engines, a rescue, a ladder, a haz-mat, 2 medics, an EMS fly car, and a fire batallion command. Today the city tried to dispatch them sending 2 engines, a rescue, a ladder, a haz-mat and a medic to a scene of a truck accident. Problem was, they only can staff 3 of the big trucks at a time (engine, rescue, ladder, hasmat) and while they can staff both medics, the guy in the EMS flycar is the same guy in the batallion and a medic and a flycar were already on a run. They just don't keep the manpower around to use ALL of their trucks at the same time. So in order to figure out what the city wanted, the guys at that station had to wait for the other stacked dispatches to finish, so they could call back on the frequency to see what equipement they wanted where.
While a central dispatch is a good idea, if it gets too crowded you start running into other issues. I would prefer dividing the county up in to 3 or 4 areas and have them mutual aid each other.