Just got back from a 2 week visit to relatives in Oz. Although I didn't go motorhoming while I was there, I thought you might like to hear about the state of the situation that I was able to get from both observations and local magazines.
Firstly, it seems that trailers (known locally as caravans) are still the main type of MH used. They are usually pretty small by our standards (16 to 24 feet) and usually pulled by a small SUV or even the family car (over short distances and no big mountains--remember that the highest mountain in Australia is just over 5,700 feet). This is something that my own family did when I was young--rented a caravan and pulled it behind our car from NSW to Queensland or wherever.
Morohomes are now getting more popular, though they are mostly class C models between 20 and 26 feet and are VERY expensive by our standards. For example a Mercedes Benz Sprinter (22.75 feet 2.2L turbodiesel) lists for Au$100,000 (US$88,000).
There are also a lot of class B's and home made conversions on the road (some well done, some really cheesy!)
Fifth wheels are just starting to make some inroads, but are limited by the lack of large American-style pickups able to pull them. Because Australia has nowhere near the interstate road systems that we enjoy, most vehicles are smaller than here. Also gas prices at the moment are about Au$1.20 per liter which converts to about US$4.25 per US Gallon.
There are a few models of larger class A's on the market, but enormously expensive and not that popular due to most campgrounds not being able to accept anything much over 30 feet.
All in all, the MH picture in Australia seems to be much more like that in Europe than here--small units being used for short vacations.
We really are spoiled!!! (and loving it!)
2007 Winnebago 26P