No, not possible afaik. O2-SIM isn't an included iPhone-T-Mobile SIM, so no chance to get that running.
My point is that I have a german O2 contract. One good thing of it is that I can also use the T-Mobile network for free with my SIM. Now assuming that I would have a DE phone, would I be able to use my SIM, I mean would I get the T-Mobile network? If yes and if the simlock is in the BB, is there a possibility to "change" the BB of my US iPhone to the DE one (doing a restore from the DE 1.1.2)?