As an AA PLT on an AA codeshare LAX-SYD-LAX (booked through a travel agent), I was able to get my QF record locator by calling QF. Once I had that, I could change seats through the QF web site (scored 80A on the A380, which is an exit row-like seat but isn't charged for like an exit row). I also had the option to buy exit row seats through the web site.
I think that non-elites can't reserve any seats more than a week in advance on QF (at least in Y), so AA PLT seems to get the same recognition as a QF oneworld Sapphire.