Matthew on arrival into Sydney from LAX you can listen for the last 150 NM or so on the Australian Satellite Feed. Aircraft appear of this feed once they are in VHF range of Sydney. Once the aircraft is handed off to Sydney approach move across to the Sydney Tower & Approach feed.
For a flight leaving Sydney for LAX start on the Sydney Tower & Approach feed. Once the aircraft is airborne switch to the Australian Satellite Feed which will cover the departure frequency and then Brisbane Centre until the handoff to HF on either 8867 KHz or 5643 KHz.
Cheers,
Mark