I saw a thread that got totally out of hand about this.
1) Test to prove aGPS doesn't use your cellular radio (or data over that radio)
Turn off your radio (turn on airplane mode), then use GPS (like the google maps, field test won't start without the cell radio on). It works =
aGPS doesn't use cellular radio for data.
2) A little info on GPSID on Windows Mobile and the nature of aGPS on the Vogue
The GPS uses the Windows Mobile GPSID, which is configured on COM4 by default. The nature of this is that it does have a cache of
NMEA data, but this data is being updated with the radio off.
The GPS must be brought into a cold start.
3) Test to prove that aGPS is being used to get or make the NMEA data accurate enough for software
Shut off your Location, Settings> Phone> Services> Location Settings> Get Settings...
aGPS uses it's own radio chipset to receive data from an aGPS server.
4) Conclusion
aGPS doesn't require a cellular connection, but does require a connection to an aGPS server (of course), and communicates with this aGPS server over a chipset which is independent from the cellular radio chipset.