Sadly, I doubt a CL-415 would do much in conditions like on 7th. In those conditions generally only two things stop going fires - either the fire reaches the sea or the weather changes.
Early spotting and immediate effective attack is about the only way to control fires on those extreme days. In my CFA days I remember being constantly reminded that if you didn't have control of a small fire on an extreme day very smartly it was going to be a major fire very quickly.
The guys on the ground, the SEAT pilots and helo pilots have been doing a tremendous job - however unfortunately once the fires are going there is very little that they can do. Increasing the fleet of that type of aircraft and dispersion to reduce initial attack times would probably be far more effective in Victorian conditions than bringing in large capacity fire bombers like the CL415 and the DC-10.