The fact that Toronto was one of those cities is not very surprising, given that it already takes in most immigrants in general. Immigrants who speak English and French, like all other immigrants, try to settle in Toronto. As for Ottawa, the fact that it is the federal capital and close to Quebec means that French-speaking immigrants very much tend to settle there.
I know that efforts are being made by the Atlantic Canada Opportunities Agency to increase the number of French-speaking immigrants to New Brunswick. Of course, the arrival of immigrants is a relatively recent phenomenon in New Brunswick. It's evolving. Most immigrants obviously settle in Vancouver, Toronto and Ottawa because those three cities already take in most immigrants, regardless of language.