There are several operators of airtankers in Canada.
http://www.conair.ca
(B.C. Grumman Firecats (Tracker), DC4, DC6, requirements: Fixed-wing Pilots
2,500 hours total time with 500 hours multi engine PIC, Airline Transport Licence, Current Instrument Rating.)
http://www.airspray.com
(Ab, CL 215, Douglas B-26, Lockheed L-188 Electra. Not sure req'ts, most likely similar to Conair)
http://www.buffaloairways.com
(N.W.T. CL-215, PBY Canso, DC 4, check website for req'ts)
Sask (Trackers, CL-215),
Man (CL-215),
Ont (CL-415, DHC-6), and
Quebec (CL-415) all crew their own aircraft, so you would need to contact the human resources dept. of the respective Dept. of Natural Resources.
Due to the small number of a/c, there isn't usually a lot of movement, especially in the government run operations. Your best chance is with someone like Buffalo, or Airspray.
You need to remember that the job is seasonal, and that you will spend quite a bit of time away from home. The job is challenging, and can give you a lot of satisfaction. It can also be quite boring waiting for the next flight. If it rains, then you get to sit and wait until it dries up again. It's truly fun and challenging work, and if you're persistant you'll get in.
Good luck
Cheers
Randy_G
If you can't stand the heat...
then turn up the air conditioner !! 
[This message has been edited by Randy_g (edited 16 January 2001).]