AA always issues BP for QF connecting flights, and QF at LAX now uses those AA-issued BPs (for years QF would tear them up and reprint BP on QF stock). She can use the airside transfer bus from T4 to TBIT, to avoid going landside. Sometimes security will see AA on BP and tell you to go to T4, if this happens just remind them that flying QF to SYD. All very convenient, there are some advantages to staying within an alliance sometimes.