Auran Trainz Railroad Simulator 2004: http://www.auran.com/TRS2004/, Auran Trainz (older product): http://www.auran.com/trainz/
Compilation of Australian Content
Trainz of Oz: http://www.e-wire.net.au/~eb_batho/
Content Creators with an Australian focus - Not a comprehensive list (yet )
Rob Shaw Art & Visual Design: http://railsimpro.com/rob/index.html - SA, Vic
Pikkabird: http://www.pikkarail.com/ - NSWGR 47 Class, QR 1502 Class (plus lots of BR & other stuff)
Spooney's Trainz Creations: http://users.hunterlink.net.au/~djrjc/ - NSW content
Everleigh Workshops: http://www.users.bigpond.com/david.marian/trainz/trainz.htm - NSW content
Razorback Railway - The Living Railway: "The Razorback is an Australian themed route that now covers some 150km of track with a wide variety of scenery. typical of the Australian landscape, You are able to find yourself in wide open plains, parched desserts, lush rolling countryside and grasslands, dense forests, sheep and cattle grazing areas and the like. The route is entirely fictional but sometimes it appears to have a life of its own."
South Australian Layouts
Trainz of South Australia
Redbull's Trainz -- Adelaide-Noarlunga Layout
Discussion group for creators of Australian content for Trainz. Site includes self-managed databases of Aus content by state. All welcome.
Send me (F224 aka Peter8) a PM to add to this list.