What about general third party lounges or lounges that are operated on behalf of a member airline.
For example, if I was flying AA from Mexico to Miami, I could obviously use the AA lounge. But what about the Aero Mexico Lounge that, according to the oneworld website, is "Operated by a third party on behalf of: LAN".
oneworld Emeralds can access any oneworld lounge but I'm not sure of the rules governing third party lounges. The oneworld website says "A non-affiliated third party may operate some lounges on behalf of the individual airline. Access to some lounges operated by third-parties on behalf of oneworld member airlines may be restricted at some times."
I'm specifically looking at a port where the lounge of the airline I'm flying on doesn't have showers, but a third party lounge (operated on behalf of another oneworld airline) does and I'd like to use it for that reason.