A hub for large regions in the case of cities under 1 000 000, but cities over 1 000 000 are generally just considered hubs regardless of proximity to other hubs.
Halifax is the hub of the Atlantic, Montreal is the hub of Quebec, Toronto is the hub of Ontario, but being that metro Ottawa is also over 1 000 000 people, it's clearly a hub in its own right. Winnipeg being the largest city for 1000 km east or west in Canada makes it a really important hub, and Alberta's cities are both hubs of generally equal importance. Vancouver is the hub of Canada's Pacific Coast.
Quebec City may also be a hub, but I didn't include it as such, as it's really not that big of a deal