Immigrants benefit all regions regardless where they live, though more where they physically live. The simple reason is taxes.  Taxes get redistributed though various programs across cities, provinces, and the country.

However, there's a growing gap between the big 3-4 cities and the rest of Canada, especially small town and rural areas.  A big proportion of immigrants come from places which are already better than rural or small town Canada. It is hard to keep them there for long without some additional incentives.