There are very few things bitter rivals and AT&T have historically been able to agree on, but believe it or not, the two cellular giants are essentially banding together against quite possibly the greatest threat their wireless industry duopoly has ever faced.T-Mobile, which was once the nation's distant fourth-largest wireless service provider, has already managed to shortly after being allowed to , setting its sights now on trumping Verizon as well. While that's unlikely to actually happen anytime soon, Big Red's fears that Magenta will eventually end up dominating the ...