T-Mobile USA to carry Galaxy S II

The phone in that article showed weather for Barcelona. Is there reason to believe they were not talking about T-Mobile Europe? The US uses AWS bands, which according to the S II specs is not supported.

Here is a question. In order to support AWS bands, is any different hardware needed? Or it is just a software change to the radio?

No, a hardware change is required. Samsung's gonna have to swap out the radio for their super duper special AWS radio which frankly shouldn't take that long.