....If arriving or departing on QF at SYD, you should be able to use the free QF airside transfer shuttle. But being SYD based, I've never used it - others may be able to elaborate.
If you have checked baggage you effectively cannot use the QF airside T3 Domestic to T1 International free transfer, as you probably will not be able to go back to airside with baggage. The QF bus leaves from T3 domestic gate 15
If you have carry on only you can use the QF bus, being a QF customer on the day.
http://www.flyertalk.com/forum/ocean...transport.html [Click too open the wiki].
QF will not interline baggage on separate itinerary
QF:
http://www.flyertalk.com/forum/qanta...xceptions.html
OW
http://www.flyertalk.com/forum/onewo...d-threads.html
(posts 3 & 4 done as I was typing)