CASA wishes to have its cake and eat it too. Hence the refusal to make hard and fast rules about calls and the inclusion of the word “reasonably” in the CAR, that is obvious. it preserves CASAS right to prosecute if they feel like it in the event of an incident and the pilot doesn’t have a defence of making a set of mandatory calls. ahence the only rational response by a pilot fearful of becoming a felon is to make all possible calls.
the classic setup for such a prosecution would be a near miss between a turboprop RPT aircraft and a C172 at broken hill.