Guy I know is interested in getting an unlocked 8900 (former Tmobile) and using it on ATT.
He claims that ATT told him "Since the 8900 isn't 3g capable, you won't be able to run GPS on it."
I believed that a data plan is a data plan. There is no true "3g data plans" its purely built into the phone. I told him, if he has a data plan, he could get on the app world, buy a GPS app, and all would work fine.
gps is built in, att may lock it on bb maps but ive heard with google maps u can use it fine. gps doesnt need a data plan but to load the maps/pictures it does, so such as geotagging it should be fine without any data but for google maps it should work with edge or wifi