I found something interesting that seems to be in quite of a few of AA's domestic fare rules:
Category 4: Flight Restrictions
THE FARE COMPONENT MUST NOT BE ON
ONE OR MORE OF THE FOLLOWING
ANY AA FLIGHT OPERATED BY AS
ANY AA FLIGHT OPERATED BY B6.
AND
THE FARE COMPONENT MUST BE ON
ONE OR MORE OF THE FOLLOWING
ANY AA FLIGHT.
It looks like revenue management is preparing to launch the B6 and AS partnerships at some point.