We checked this out last year when the first season came on. They have a metric buttload of conventional freqs in UHF and VHF, and the truckers are mainly using the road LAD channels. I think I have the LAD channels listed in the Alberta section of the DB - they're fairly common among the western/northern provinces and territories.
I seem to recall that people last year were saying that they saw hammy type radios in some scenes. If that was the case, it would not be out of the question (although it would be illegal, of course) for the users to tweak the radios to operate on the VHF LAD channels at high-wattages... IIRC, you can get mobile ham radios that will do 100W on VHF. Your garden variety rental Maxtrac or CDM1250 only puts out 25-30W.
To talk back to the base station, as I recall, they use a satellite link radio. The same kind of thing has been used in some mountainous regions of Alberta where no repeater sites can be built/maintained. It takes a simplex UHF or VHF frequency as input and transmits it to a satellite, which repeats it back to a ground station with only about a 0.1 - 0.4 second delay.