This "national" stuff is rubbish. AC doesn't offer "national" pricing (other than some pass products). What they advertise with pricing is point-to-point travel. Taxes are pre-determined. It doesn't matter whether you live in Toronto, Montreal or Alberta, your YYZ-YVR ticket will cost you the same because taxes are based on point of departure - not your residency. They can advertise the same YYZ-YVR price anywhere in the country.