Based on oneworld:
Indulge yourself before departure in a wider range of airport lounges when you fly First Class or Business Class with any oneworld member airline, though exclusions apply. Customers flying First or Business Class have access to the equivalent class of lounge regardless of their frequent flyer status. First Class passengers may use a Business Class or frequent flyer lounge if a First Class lounge is not available. First Class passengers 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 airline. Access is available on the day of travel (or before 06:00am the following day), at the airport from which the oneworld flight on which the eligible customer is travelling departs.
Connecting between oneworld marketed and operated flights: First and Business Class customers connecting on the same day of travel, or before 06:00am the following day, can access the lounge when travelling between an international long haul (a oneworld international long haul flight is defined as an international flight marketed and operated by any oneworld carrier with a scheduled flight time longer than 5 hours) and an international short haul or domestic flight (and vice-versa).
Lounge access will be determined on the international long haul ticketed flight (either First of Business Class) regardless of the ticketed class of travel on the international short haul or domestic flight. You must be prepared to show your boarding pass or itinerary showing travel in First or Business class on the international long haul flight, in order to access the lounge before your international short haul or domestic flight.
You
might have access to the QF lounge at the TBIT terminal at LAX. All the terminals are connected at LAX. From T6 where Alaska is, it's a 15-20 minute brisk walk through the airside tunnel system.
I say
might because of this also on the oneworld website:
laska Airlines Mileage Plan MVP GOLD 100K, 75K, and MVP GOLD members may access
oneworld lounges when travelling to somewhere outside of the U.S., Canada, or Mexico.
Additionally, Alaska Airlines customers on Alaska Airlines operated domestic flights, connecting to or from an international long-haul flight in a premium cabin on the same day, are eligible for
oneworld lounge access before the domestic flight.
For more information, visit
Alaska Airlines' website.
The rules seem to contradict themselves on the AS website.
AMEX's Centurion lounge is located below the oneworld lounges at TBIT. So it's also a 15-20 minute brisk walk from T6.