You can add the Australian public holiday's into your Outlook calendar through the Outlook Tools menu. Follow the instructions below
In Outlook 2010 select the File tab then select Options. Select the Calendar option and then select the Add Holidays button.
Ensure that Australia is selected and click "OK"
In Outlook 2007 go to the "Tools" menu and select "Options..."
Select the "Preferences" tab and click on "Calendar Options"