Is BA too dependant on LHR as a hub?
Is AA too dependant on DFW as a hub?
Is UA too dependant on ORD as a hub?

The list could go on and on. IMO, this could have happened to any of these airlines at their hubs. The airlines operate these hubs because that is where the majority of their business originates from. YUL was once AC's primary hub, but as YYZ grew it took over that role. We have been told that AC is hoping to use the new EMB and other types to offer more point to point services that bypass the high costs of YYZ, but it will still remain as the primary hub of the airline.