As for the military aspect, I think you are absolutely right. If a Russian or Chinese warship were to dispute Canada's sovereignty, we would have to hope that applicable diplomatic agreements were already in place. In contrast, if it were a merchant ship, I hope that the situation could be resolved before we had to resort to that.
Ultimately, however, I think that if we are serious about Canadian sovereignty, we have to do something. If we do not intervene in a case like this, then we are not sovereign.