Just to provide further clarification, you book a round-trip award on a single partner carrier (i.e. Cathay Pacific OR Qantas OR Korean)--no mixing and matching, as described above. Where Alaska comes in is: If you cannot find a flight on the partner carrier leaving directly from your originating city, then Alaska will provide you with a connection to the international departure gateway. For example, if you are looking to fly Qantas from Anchorage, since Qantas does not serve Anchorage, the Partner Desk agents will book you on Alaska to LAX or San Francisco and then Qantas from there to Sydney. This does not cost any more mileage.

Unfortunately, the award option between North America and Australia on British was pulled about two or three years ago. I was fortunate to have been able to book it before the award was removed, and it was indeed quite the experience (and an exceptional value). However, I look forward to trying Cathay one of these days, since reportedly their product is superior to BA's. Cathay would still be an excellent value.