Big, quite simple my friend. Their ad doesn't generate any sort of economic boost to the Canadian economy, or that within Toronto. The advertising dollars will be the only real boost, which would outweigh the cons, that being Canadians spending their money on company's based in another country, as opposed to Canada.
It's like toursim. The Canadian government would rather see you remain in Canada and travel within the country, thus spending your cash within the country, as opposed to flying to Cuba or France for the holidays.
Not ragging on the BHB or nothing, but just pointing out that it's nowhere near the significant boost to the economy that you term it is.
As well, it seems the PGA will be organizing an event specially for Toronto this year, aside from the Open.