Binos,
As someone who was working in Cairns at the time of the changeover from Procedural Approach to Radar Approach (actually the last person to be rated on Proc.), I can vouch for your summary of the situation at the time.
The introduction of radar to CG and CS was based on the amount of traffic, not the nature of the airspace nor the relative positions of the sun and the moon. RHS himself seemed to have no apparent difficulties operating in Procedural 'C', from what I observed.
sep
Check your PMs.