My hat's off to all involved with the fires in NSW !!!
A little info on the CL-415, from what I have personally seen working beside them (I fly in Canada). If you have a good water source close by, they can put lots of water on the fire very quickly. Their tank holds approx 5700 litres. Where they lose out, is when they have to go long distances to pick up water. The CL-415 can cruise at 180 kts, but compared to a P-3 Orion, or other converted ex-military, ground based attack aircraft they are slow.
Experts, well the definition of an expert is ex= has-been, never-was, spurt= drip under pressure !!!
The triangular shape of a pine, spruce, etc makes it incredibly difficult to hit anything underneath. The water just runs off the tree, completely missing anything underneath. Whereas working around the leafy trees the leaves are blown out of the way, so the water can get to the ground. I would suspect that the gum trees would be similar. One major difference though, is the amount of oils, resins contained in the gum trees compared to trees native to North America. Your trees hold quite a bit more, which I suspect would cause the fire to spread very rapidly, and get hotter, faster than ours do.
Oh John, if you're ever looking for some fun, try coming to this side of the Pacific. We'll get you on a 200' line bucketing in the mountains at 5,000' with an oat of 30+.
Cheers
Randy_G