Originally Posted by KARFA

If on AS, then your inbound BA f bp should get you access to the QF F lounge in TBIT and the AA flagship in T4. Once airside you can walk between TBIT, T4, and T6.

Originally Posted by bhomburg

The AS F ticket won't but your BA F ticket would get you into the Alaska lounge. The OW rules are very clear on that point:
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.
AS's own policies as well: When traveling on a paid First Class or a First Class award ticket on OW member airline with at least one international flight greater than 5 hours in length. The First Class ticket must be on the international segment.

The Qantas F lounge is much nicer than the Alaska one, and you would have access to that as well.