Members of oneworld airline frequent flyer programmes with the equivalent of oneworld Emerald or Sapphire tier status can use lounges offered by oneworld airlines when departing on any flight marketed and operated by any oneworld member airline, regardless of cabin class being flown (exceptions are noted below).
...
Emerald and Sapphire members may invite one guest to join them in the lounge. The guest must also be travelling on a flight operated and marketed by a oneworld carrier.
...
The following exceptions apply:
1. American Airlines and Qantas offer programmes enabling customers to pay to gain access to their lounges. These programmes are not part of the oneworld agreement, and members of these programmes are not entitled to access lounges under the oneworld agreement.
2. American Airlines AAdvantage� members, regardless of their tier status or class of travel, cannot access American Airlines lounges when travelling solely on North American flights within or between the U.S., Canada, Mexico (except Mexico City), the Bahamas, Bermuda and the Caribbean. For more information, visit, http://www.aa.com/i18n/travelInforma...miralsClub.jsp
3. Qantas Frequent Flyer Gold members, regardless of their oneworld tier status, cannot access Qantas Domestic Business Lounges.
4. Qatar Airways Doha International Airport Premium Terminal is excluded.
5. Qatar Airways Premium Lounge at LHR Terminal 4 is excluded.