I am AAdvantage Exec Platinum with American Airlines. I've booked a Qantas codeshare flight, operated by Emirates. Which lounge(s) can I use at Heathrow (Terminal 3)? I assume I can use any Oneworld lounge, including the Qantas one. Can I also use the Emirates lounge? Which lounge can I use on a return journey from Dubai?
Although in the end I didn't actually try, it seems the answer is no:
To be eligible, you must be departing on a flight that is both marketed and operated by a oneworld member airline.
It also appears that my OneWorld status didn't allow First class check-in or early boarding either.