I could have sworn immediately after the announcement SE held a conference and they specifically already said they wanted to bring it to the 360 but they needed to iron out some things, assuming with the online structure or whatever with the 360.
I think anyone following this game was aware it was coming, especially when Tretton said "at launch" when he talked about exclusivity.
However i think its a rare case where times exclusivity had nothing to do with the dollaz and more to do with working out infrastructure.