I believe from my reading the CAR 5.55 and the CAO 48, you can fly as much as you like on private operations.
However, you must take into account any flight and duty time performed on private operations (48.0.1.3) as it may reduce the flight time available to your employer or cause you to exceed the limitations imposed by CAO 48.1.
CASA appears to be relying on a ruling in WA to say that any private flying conducted after a period of employed flight and duty shall have the same limits as imposed by for 48.1, i.e. 8hrsFT/11Hrs duty.
I believe this is an incorrect interpretation of the CAR and CAO in that there is no limitations on private flight or duty occurring after a period of duty for which CAO 48.1 has limitations. CASA have not given any directions for any limitations on private flying as allowed by CAR 5.55. CASA have for Chtr, AWK and RPT via CAO 48.1
However, you may not be able to be rostered the next day as you may not meet the rest period on the ground nor have available flight hours to remain below the 7, 30 or 365 day limitation or duty hours to remain below the fortnight duty limit.
If you fly to work, that duty and flight time will reduce the amount of flight and duty time available to your employer.
take into account any flight and duty time performed on private operations