Answers to the questions:
1) Yes, it is, technologically, possible that a provider can detect the phone your SIM card is in. Don't know if AT&T will do anything about it though, most likely they won't, since if you /do/ use any data over the card, they'd be able to charge standard rates, giving them more cash.
2) There is little difference in ANY of the streaks, there was rumour that the White one had something done to it's internals, but no, the numbers you see related entirely to the Android OS installed on the device.