Airservices say, "As part of the transition to the Global Navigation Satellite System (GNSS) by 4 February 2016, the Airservices Navigation Rationalisation Project (NRP) is switching-off 179 ground-based navigation aids, on 26 May 2016.
The navigation aids to be decommissioned include, non-directional beacons, VHF omni-directional ranges and distance measuring equipment.
GNSS is now the primary means of navigation for all instrument flight rule aircraft, which will be supported by the Backup Navigation aid Network, also known as the BNN."
Then looking at
The Backup Navigation Network | Airservices They say,
"The remaining network of navigation aids will form the
Backup Navigation Network (BNN) . The BNN will be maintained and monitored by Airservices to support a GNSS contingency mode of operation, in the unlikely case where a pilot is unable to access the satellite service.
In 2004, the navigation aids that form the BNN network were selected by industry after extensive consultation, and following further industry validation in 2010, 14 additional navaids were added to the list."
They do not actually say what nav aids are used for BNN, and Australia is a large country for full radar coverage.
Also, if NDB, VOR and DME is not now used in Australia, does that mean that Aus registered a/c could have some open holes in the panel if they do not fly out of the country?