Hello -
If you use the Standard Shipping Module in Virtuemart, then it can handle any country or any set of rates. You can use the Standard Shipping module to configure default for Australia and the rates for Australia.
Currently, we support the Standard Shipping Module (any country, any set of rates as long as configured), and USPS for U.S. processing. We are close to wrapping up UPS as well. We don't currently support any specific Australian shippers if you are trying to interface with them using an API. We would like to support them in the future, and it is on our roadmap. If you need it sooner, please PM me if you are willing to sponsor custom code. As noted, you can always configure rates to work in the Standard Shipping module.