Canada may have two official languages, but that doesn't mean everyone in the nation fluently speaks both French and English. Bilingualism (speaking both French and English, which is how the term is often applied in a Canadian context) is actually somewhat rare across Canada.
Going from Western Ontario all the way to British Columbia, one would only have a 0-9% chance of meeting someone who is bilingual, as the attached map demonstrates. It's not like these provinces are known for their bilingual nature, but that's a huge chunk of our nation's geography that is predominantly unilingual.
That's not the case in Montreal, where there is around a fifty percent chance of running into a bilingual person across the entire island. Certain areas are shown to be even more bilingual, with the urban core of the city shaded with a 70-100% chance of bilingualism.
Interestingly, half of Ontario (the side closer to Quebec, of course) is more bilingual than I would have guessed. Ottawa also boasts some very-bilingual areas, and there are spatterings of bilingual communities in Atlantic Canada as well.
No one really needed to tell Montreal that it's the most bilingual city in Canada, but it's always nice to hear, and it's especially interesting to see how the rest of the nation compares. Obviously they all need to catch up, but it'll take a while before everyone can read this article without any difficulty.
For a closer look at the Bilingualism in Canada map, take a gander below.