The CL-515 is still a concept and while the -215 and -415's are good planes they also fill only part of the role. For example they can haul some people but not alot due to the water tanks and scooping design.
Coulson has 3? C-130's certified for civilian use and is trying to source more as I understand it. They have contracts in Australia for seasonal use but currently no Canadian contracts that I am aware of...not that they don't ask. They do provide heavy lift helicopters but that's different from tankers and the Martin Mars hasn't been under contract for several years now.
There are occasionally some C-130's that come up...and they have a long history of being used going back to the old C-130A models in the US but the challange with many of the military surplus units is ensuring enough service records exist for not just airframe but also parts used to get certify...and its not a fast process. Even the US who has Federal to State agreements has had issue with the transfer of C-130s to the USFS although there are also many other sides to that story.
The Dash 8 Q400 (Conair), the RJ-85/BAe 146 conversions (see Conair/Neptune Aviation) are starting to show up to replace the older frames. AirSpray was re-building entire wing assemblies to address issues with the L-188 fleet and Buffalo Airways runs a mix of Territory owned and company owned airframes.
Coulson has been growing both their US, Canadian and Australian presense. See here for the US fleet - not all of which are in Canada.
Fleet — COULSON AVIATION
Any then you get into the Air Trackers...
Big issue is no one airframe is good for everything. Having a group of 4-5 AT-802's coming in tree top can be great for precision bombing but they don't work well if you don't have airstrips (there is a scooper version though). CL-415's are great if you have scooper lakes allowing for fast drop cycles...I've seen under 5 minutes for drop, exit, load, approach and drop....but they're slower and lower capacity than some of the others. Electras or RJ85's are much faster and are good for long line drops and/or water slugs to break the tree canopy. And then there is what they use in the USA where frankly we don't have the Stratigic Air Command runways to operate off of so don't use the DC-10's, -737's, MD-80's in use there.