ESU have plenty of steam sounds in their library. That said, "Australian" specific steam sound may not be there... That said,another key advantage of ESU (and perhaps other brands? I don't know which... maybe QSI??) is that you can pre-load the ESU decoders with any specific loco sound. For example, there are (nominally) operational SAR Rx-class steam locos that you could record off and then load onto a ESU sound decoder. I don't think many other decoder vendors enable you to do that.
However, as pointed out, many Aussie diesel locos have the same engines and components as many US locos and hence easily used if you buy the correct decoder with the correct sound files.
SA_Trains. Understand that, but without going into details of the few ESU steam sounds that I have heard, I really felt disappointed. Certainly the user ability to download ones own sounds are an advantage, but something I am desirous of getting into primarily for the reason I know of some who have said its not that simple, yet those with experience say its no big deal.
I understand it is also possible with QSI decoders & I did purchase one of their programers for that purpose, it is probably worse than the ESU programmer to figure out. The other aspect is that I am really no longer convinced with QSI products especially their after sales service. I purchased a Revolution decoder & was fairly happy with it, but it lasted a mere 1 hour at the most in operation before it shot itself with an on board short within 2 months of the purchase. It was sent back to QSI for replacement & they accepted that it was a decoder fault but still waiting & that was around 2 years ago now not long after the revolution was released. A further promise of replacement with their new Titan has also come to nothing, I suspect its run into an iceberg & now part of a Titanic range. Watching the QSI group, also shows a lot of issues have arisen with them as well.
Even though you can get the Oz diesel sounds by using generic prime mover US sounds, in the likes of Tsunami's & I do have one in my TOR 42, there is something not quite right regarding the sounds but I am able to live with it, as I think a heck of a lot has to do with the speakers as well.
If nothing else, I am very glad I did not rush into buying sound for all my models, & as I await the TCS sound, that will also be a test case before any further commitment.