From speaking to a few CFA guys today, there seems to be a media beatup (No - not possible
) on the usefulness of the larger type of tankers. One of the problems associated with these aircraft is their refill time. Via hose it can take a very long time - up to 24 hours, and to scoop airborne can be a problem. Port Philip bay is often too rough for airborne refills. The difference between Aus and many other places is the availability of long, smooth lakes. Victoria is sadly lacking in these that are suitable.
These guys seemed to agree with Farmer Pete about more aircraft more often, rather than one dig dump less often.
This info is only from a few guys and I'm not saying it is correct, just putting it out there for discussion