Upvote:3
It seems there are:
(a) a Discovery Pass, which allows unlimited train travel within 'New South Wales' (including between Sydney, Brisbane, Melbourne and Canberra) β but not including Cairns.
(b) a Queensland Explorer Pass, which allows unlimited travel on most Queensland rail services.
(c) a Queensland Coastal Pass, which allows one-way travel between Brisbane and Cairns (or vice versa), with an unlimited number of stops en route (but only in one or other direction).
So with passes, from Sydney to Cairns you would need (a) and (c). However if not making various breaks in the journey, a 'regular' train ticket or tickets might cost less.