It seems that T-Mobile testing iPhones have an A5 processor

[From Hans] It seems that T-Mobile testing iPhones have an A5 processor according to the BGR website. "Additionally, the front of the white iPhone pictured looks a little different from the photos of the retail white iPhone 4 that surfaced recently — specifically, the proximity sensor has changed on the retail version. Combined with the fact that it wouldn’t make sense to release an iPhone 4 on T-Mobile at this point in time, we’d wager that Apple is just testing the new T-Mobile-friendly radio with its current iPhone 4 hardware, possibly in preparation for integration in a future device" Read in full.