In no area have I found anything regarding Ford using A-GPS. I'm only finding data that this is used in cellular platforms only. Do you have any sources for this information, as I'm curious to how it's linked and functions on the Ford Sync platform.
Ford may be using dead reckoning, which would calculate off speed signals, but that should only kick in when you're in a tunnel, parking garage, or in a forest. There are multiple other Ford forum posts that recommend disconnecting the negative cable and letting the car sit for 1 hour, and this has resolved multiple issues (pre and post tire recalculation).