So cloud can't exist OCTA? Or do we only need ATC when it's cloudy? Maybe CTA to the ground everywhere, just in case it's cloudy somewhere? How many thousands of times in Australia has an IFR aircraft flown in cloud OCTA in the last, say, 70 years? And how many of those, besides these two, have collided? Hmmm, maybe alerted traffic (under both systems) might have something going for it?