Here's what the legislation says regarding category A & B
"SCHEDULE 4
STORAGE REQUIREMENTS
1 Longarm licences for category A and B longarms
(1) The firearm must be stored in a receptacle—
(a) which is constructed of hard wood or steel
that is not easily penetrable; and
(b) which, if it weighs less than 150 kilograms
when it is empty, must be fixed to the frame
of the floor or the wall of the premises where
the firearm is kept in such a manner that it is
not easily removable; and
(c) which, when any firearm is stored in it, is
locked with a lock of sturdy construction.
(2) If more than 15 firearms are stored on the
premises where the firearm is stored, the premises
must be fitted with an intruder alarm system—
(a) the installation, maintenance and operation
of which complies with Australian Standard
2201.1:2007 (as amended from time to time);
and
(b) which, in the event of an intrusion, activates
an audible alarm warning device and an
external visible alarm warning light.
(3) Any cartridge ammunition for the firearm must be
stored in a locked container separate from the
receptacle in which the firearm must be stored."
It does not actually mention keys at all
Only the legislation regarding Category C & D firearms mentions regulations regarding keys