"The carrier allegedly threatened to drop BlackBerries entirely from its network when RIM protested the limitation, according to the source."
No way. Does any one seriously believe ATT would put itself in a position to be the only provider in North America not to sell Blackberries. They would lose a helluva lot more customers than just those who want full GPS capability. Why risk losing that customer base when when the initial enthusiasm for the iPhone will soon wear off (if it hasn't already) and it will be nothing more than than just another smartphone.