Recently, the Bloc Québécois (BQ) irrelevantly asked the federal government to let Quebec applies Bill 101 to federal institutions located on its territory. Let's not be surprised by such a pathetic publicity stunt from the BQ.
Gilles Duceppe, its leader, argued that under the Canada Labour Code, the paragraph (1)(a) of the article 178 stipulates that a worker's wage should "not [be] less than the minimum hourly rate fixed [...] by or under an Act of the legislature of the province where the employee is usually employed". Hence, the laughable necessity to allow Quebec to make French the only language of communication in federal institutions located on its territory, according to him.
The issue of languages and labour are not to be put in the same basket. After all, the federal government lets the provinces train their respective workforce through professional associations, for instance, by following some basic rules dictated by Ottawa. All in all, the share of power between the two level of governments is relevant in labour, because provinces actually have people who live and/or work within their respective boundaries.
As for languages, things are different.
Obviously, Duceppe has been trying to act as if the use of French in Quebec was seriously threatened. With a small English-speaking population mostly concentrated in Montreal, it's obvious that most Quebeckers already have what they want from our federal institutions: an adequate service in French. So, what's the point to complain? In addition to that, more than 60% of Anglo-Quebeckers are billingual.
Needless to say that all federal civil servants working in Quebec are not trying to impose English. In fact, anyone of them understand the importance to respond in one of Canada's official languages used by a given citizen. Besides, Duceppe's idea violates the Official Languages Act's article 12. Regardless of the province in which you are, this article clearly requires all federal services being given to you in both official languages.
Evidently, the reason why federal services are offered in both official languages, it's because they have to satisfy all Canadians, even when they travel in another province. For example, if an English Canadian wants to fix a few things with his declaration of revenue while visiting Quebec, he doesn't expect Bill 101 to have precedence over the Official Languages Act in federal institutions.
Of course, the labour language is technically French within the boundaries of Quebec, but some reasonable limits apply. For instance, Duceppe should face the fact that federal institutions are not under the jurisdiction of Quebec's National Assembly. There might be federal institutions in Quebec, but they operate under the Official Languages Act and not Bill 101.
People might not notice that Duceppe violates, in a very simplistic way, the Official Languages Act, but they certainly will notice that he's just ready to bite any bone just to look good in public opinion.