Just checked on the Web (NSW RTA):
Unregistered Vehicle Permits (UVPs)
An Unregistered Vehicle Permit (UVP) is valid for up to 28 days and allows you to drive or ride an unregistered vehicle on the road network for a specific journey, including:
A single journey from A to B.
A return journey from A to B to A.
A number of defined trips to be completed within 28 days, eg from A to B to C to D.
For a specific purpose over a number of days up to a maximum of 28, eg for harvesting during a defined period.
UVPs provide only limited access to the road network. They are not intended to cover the regular use of a vehicle on a road or road-related area (eg footpaths, nature strips, public driveways, public carparks etc).
A UVP must not be used as a substitute for full registration.
Vehicles carrying a commercial load and vehicles exempt from registration cannot be issued with a UVP.
UVPs are valid in all States and Territories except Western Australia.
http://www.rta.nsw.gov.au/registration/unregisteredvehicles/uvp.html