Just to add to the controversy, I have personally had several discussions with CASA in the Tamworth Office in recent times over this very para (10.1) in CAO20.18, viz:
"10.1 In the case of a charter aircraft etc..... it carries, or is fitted with, under subregulation 207 (2) of CAR 1988, must be serviceable etc...."
The interpretation from Airworthiness in that office (which resulted in a directive to change the wording in an Ops Manual I had written and submitted to them) is that "all instruments and equipment" in fact, means only those instruments and equipment which CASA has directed be fitted to the aircraft in accordance with CAR 207(2). That would not necessarily, for example apply to a second VHF COM, NAV or GPS if it were fitted, or any other equipped not fitting the bill as being directed to be fitted under the CAR.
I must admit I'm still not totally convinced, but I am not a lawyer either. The inclusion of the reference to CAR 207 (2) in that particular para (10.1) is however a relatively recent change to the Order (Jan 2013 I believe).
Just sayin"....