avec00,
You obviously spoke to a rarity among AC Club staff - someone who knows exactly the access rules in association with Oneworld travel. The info they gave you is correct although don't expect to get exactly the same answer from any other AC

BTW, is your BNE-SYD same day as LAX-BNE or do you have a stopover in BNE? Normally flying domestically in Australia in BC doesn't allow you access to domestic terminal QANTAS clubs but if you have flown into Australia on QF BC you are allowed access to all QF lounges on domestic segments of the itinerary. I think you'll find the info on the QF website under their BC product description and it might be worth printing it out, although the QANTAS Club staff seem to be a lot more consistent in their knowledge of the rules.