For the amount of flight operations in Australia, mid-airs are over represented, our system is vetted by many third world airspace. ADSB OUT AND IN makes a difference. Having recently avoided 2 different conflicts in short succession due to ADSB IN, I am concerned by the robustness of Aus airspace.
Useless if one of the aircraft is not fitted with the equipment required. Backup ACAS systems are great, but it would be interesting if the Pawnee had ADSB at all. In the US this has been a problem as well, some operators get used to the ACAS warning them and spend less lookout time for the aircraft not fitted or with inoperative systems, or just turned off, it's been a factor in more than one collision of late.
As for two runway operations OCTA, if something is blocking LOS then both radio and ACAS may be blocked as well.
PS even if there was a single runway there's still the chance with a hump in the middle you could get two aircraft taking off in opposite directions, so its not really a two runway issue, it's really a communication and lookout issue.
I don't think we will see a report eventuate on this accident.