I think, at the very least, the federal government would have to provide a modicum of French-language services for French-speakers within the province of Quebec.
I don't know what the policy was prior to the B&B era, but if the government was already doing that(French services in Quebec), that's arguably a form of official bilingualism, even prior to Trudeau making it a national policy.
Now, if you're refering to the Trudeau policy, in practice I think you could easily jettison French-language services in places where there is only slight French population, and/or the French residents can all speak English.
BUT...
That becomes politically and socially problematic if and when the Quebec government decides they wanna rain hellfire down on the rights of the English minority. Because if the feds object, Quebec can always come back with "Well, no one does sweet bugger-all for the French in Kelowna, why the hell should we do anything for the anglos in Trois-Rivere?
Coast-to-coast bilingualism does seem somewhat absurd at times(and I say this as the scion of Franco-Manitobans who definitely benfitted from the policy), but, in terms of national cohesion, there probably weren't many other options, post-Quiet Revolution.