Thank you for your question.
You have to draw a distinction between theory and reality. Although it's theoretically preferable to apply the linguistic territoriality model in order to promote the development of French, we're prevented from fully achieving that ideal by certain political, historical and other realities.
Let's nevertheless consider the theoretical aspect.
In theory, the idea would be first to assert that there is only one official language in Quebec, which is in fact the case under Bill 101. Then the federal government would have to demonstrate, by its actions and the services it provides through its offices, that French is the language of work of its employees in Quebec. Thus the federal government would model its policy on that of the federated government of Quebec, in this instance, and on those of the other federated governments in the other provinces.
As I mentioned earlier, there might conceivably be a way to expand that somewhat so that the federal government could establish policies supportive of French in francophone areas outside Quebec, essentially those bordering on it.
Consequently, under the pure territorial model, the language of work for all federal government positions in Quebec would be French, for example. In actual fact, I think compromises could clearly be made and accommodations introduced for English-speaking Quebeckers.
That being said, the principle must be territoriality. Then…