And I know for a fact that the tariffs are completely separate, so you're not violating them. The prohibition against back-to-back ticketing is the carriers' own, and as such it extends only to the carrier.

Oh, and AA-BA-IB haven't had the time to file any "joint" transatlantic tariffs or such yet (heck, all their transatlantic fares not only are still separate, but the cheaper one specifically say you can't fly on the codeshare flights operated by the other airline's metal!!)