The 802 is a capable machine for sure, though lacking in performance and very strip hungry when that tank is full, not something that would have been a problem in the Firecat (which can operate from gravel strips btw). Also, many operators are bringing 602s and Droms, not 802s.
The Trackers were also owned by the govt until 1994. The air and ground crews were in government employ until the mid eighties and there was a significant stock of spares. They are all very low time airframes and could have quite easily been converted for fire-fighting work back then (before the 802 even existed).
I wonder what the total cost of bushfire has been since then? It would be in the tens of billions, and the cost of conversion of a fleet of dedicated bombers (with further assistance provided by smaller operators) would pale into insignificance.
As an aside, most of the helicopters are actually cheaper than the rates I have seen here. The ADF has a stupid way of costing it's assets, that sees a Black Hawk costed at around $27k per hour for example. But most medium water bombing helicopters (Bell 214, Dauphin and UH-1 for example) are $5-6k per hour to the tasking authority. If a fire is near a water source or on the coast (whether urban area or not) the rate of wet stuff on hot stuff can be much higher using these machines than in any fixed wing. I'd bet it's probably even better (for a given cost) than you'd get using the Evergreen 747!