It's not an anti-trust immunized JV in the sense of the oneworld Atlantic Joint Business which allows for revenue sharing -- whether you fly JFK-LHR on AA or BA, both airlines will get a similar portion of the revenue. In the NEA, if both AA and B6 are flying JFK-LAX, if you fly on AA metal then AA will get 100% of your money and if you fly on B6 metal, then B6 will get 100% of your money (nit pick: if you fly on a codeshare, the marketing airline gets a commission). If you fly on DL, then DL will get 100% of your money. For the most part, the airlines compete.
The difference here from previous domestic codeshare agreements is that AA and B6 are allowed to coordinate schedules. How anti-competitive that is is debatable.