Yes, but "full power" has to be taken in context. Most of the Buffalo stations transmit from the Grand Island "antenna farm" out in the boonies where nobody lives. You do NOT want, or need, to crank out a megawatt from a downtown site like the CN tower, let alone having several channels at a megawatt each. It would probably fry the ATSC tuners of any TV sets south of the 401, and freak out cellphones, too. Actually, CITY TV, at 1200 watts (no, I did NOT drop any zeros) comes bombing in OK here at Dufferin+Steeles, for those of you familiar with Toronto.
Also, in many cases, it's the terrain, not the transmitter power, that determines effective range. UHF TV is sorta line-of-sight, with a bit of fudge factor.
If you put up a 1000-foot tower atop the old city dump in Winnipeg (assuming that it wouldn't interfere with the airport flight paths), you could cover a significant chunk of southern Manitoba with one station.
In the case of the GTA (Greater Toronto Area), there's a ridgeline running approximately east/west meandering between Highway 7 and Major Mackenzie Drive. Regardless of whether CITY transmits from the CN tower at 1.2 kilowatts, or 1.2 megawatts, they're not going to be received north of the ridgeline, Period, End of story.
When you get into hilly areas like Greater Vancouver (think Burnaby), the terrain is even more of a factor. A megawatt is not going to bore its way through a hillside.
In the case of Toronto, especially from the top of the CN tower, anything more than 15 kilowatts is overkill. Besides which, with the exception of CBC, most of the programming on Toronto's English language stations is American programming with Canadian commercials. Not like there's any potential audience for that in Buffalo.