In my over "One Third Of a Century" ( our son reminded me of this ) of fighting fire all over the western US I have never seen the CL 415 used. There are not that many water sources
available as in the eastern US and Canada. Western US is generally a very arid area. Water evaporates quickly where Retardant has a residual effect, as it coats fuels and retards burning even when dry.
I have seen TBM's, A-26's, Flying Boxcar's, B-17's, PB4Y's, S-2's, C-54's, P2V's and P3's. Oh yea, also the SEAT (Single Engine Air Tanker). All carrying retardant. I retired before the commercial jets were converted.
Dick Bell