Because the Canadian government "encourages" the use of diesel by Canadians, you will find a far larger percentage of diesel-powered vehicles--both trucks and cars--than in the U.S. There may be several factors creating that difference--a desire by the government and oil companies to ship more gasoline to the U.S., the ability to produce diesel more cheaply than gasoline from Alberta's tar sands, and government taxes. Unlike the U.S., therefore, diesel is readily available at every fueling station along the major NW Canadian highways no matter how small the station or the community. Interesting in a place where nighttime temps get to 50 below zero--so low that older diesels would have to be left running all night or they wouldn't start the next morning.
Once you get to Alaska, you will be back to U.S. prices, with gasoline somewhat more expensive than the Lower 48, but generally cheaper than diesel. That may be due to the fact that most of Alaska's refineries have been shut down for environmental reasons in the past 20 years. So now, Alaska ships Alaska Pipeline crude to the Lower 48 and gets much of its fuel shipped in from Lower 48 refineries. Makes a lot of sense, huh?