It's not a theoretical yes. Its the real printed policy. They will through check bags onto any if the airlines listed above under "may check bags to" provided the MCT is met and the connection doesn't exceed the maximum allowed (12 hours for international). I I have done this on 4N, LH, UA, DL and WS. Doing it in reverse is another story though. It will depend on the airline. For example even AA won't through check to AS on separate tickets.