Lot of speculation here. Just to add to it, the rumour from Helicopters Australia's engineers is that the average load for the 350B3 is about 800lt, increasing with fuel burn off.
Eurocopter products yet to challenge Bell on the fire ground? RW, the 117 is a Eurocopter product, and has become very popular, and very capable, in the NSW fires over the past 6 years. Mine was the first, six years ago, and there are now three on government contract, and between 3 and 6 CWN in use at any one time. The ability to lift up to 1000 litres (or slightly more in the case of the HeliPro machine, IIRC their 'Spray' bucket has about 1100 lt capacity), put 8 troops into the same area as a Squirrel, all with twin engine safety and a good overall performance, has made it a reliable and popular machine.
As with any machine, there is always a trade off early in the action when heavy on fuel resulting in a reduction in payload. Fixed capacity buckets such as the Bambi inevitably are cinched in 10 or 20% to allow for this, whereas the tank equipped machines, or those with DUFAS or Spray buckets can adjust the water pickup through the flight. Even the larger mediums are prone to this, I noticed more than one 214B and Huey variant with 80% on the cinch strap, and the Aircrane certainly doesn't start off with full load when it has full fuel. My Bambi is set at 90%, and when I use the DUFAS I go a bit heavier on fuel (stay out longer) and start at 70% (700 lt), but can haul 100% (1000 lt) after an hour.
The 350B3 sounds a very capable set up, and deserves support. Western Australia has suffered from an anti helitack mentality for years, any opportunity to break the nexus is more than welcome, IMHO!