Originally Posted by CrazyJ82

There is a huge and rapidly increasing amount of bad information in this thread. Once and for all:

OP is entitled to lounge access as a CX SL. In this situation, CX treats the JFK BA lounge as a contract lounge and can extend the normal MPO rules, including access for SL. No sweet talking or exceptions required. (Unless you want to try to bring in a guest.) This is different from a situation (like HKG, BKK, SIN, NRT or others) where CX operates or contracts one lounge but other oneworld options are available. In that case, CX SL can access only the CX-designated lounge.

OP's entitlement applies even though the flight is AA coded because the rules say the issue is operating carrier (CX), not marketing carrier.