http://www.airservicesaustralia.com....1-Aug-2006.pdf
Expectation as per the main text is that you would follow flight planned route and alt. However see note 2 appended to the main text also indicates that last clearance alt could be appropriate... The regulator seems to have a bit of 2 bob each way on this crucial issue. The way i read it though is that following the cleared alt is referring to terminal area ops on descent where the cleared alt is less than flight planned alt and resuming flight planned alt is not practicable.
If it were me after a planned waypoint and planned alt change with lost comm i would be at flight planned alt tracking to flight planned destination conforming to appropriate hemispherical alt. Having said that the purpose of the procedure is, explicitly,
to make ATC and other traffic aware of the pilots most likley actions.