There is always a debate on the meaning of linguistic duality.
I know that the federal government uses the expression “linguistic duality” to refer to bilingualism and the two official languages.
In New Brunswick, linguistic duality also has a political and administrative meaning, in that it designates linguistically homogeneous structures or structures that enable both linguistic communities to manage matters that affect them.
For example, in education, when we talk about linguistic duality in Canada, we talk about two school systems: the francophone school system and the anglophone school system. These are dualist systems, in the sense that both communities can manage their educational institutions.
In health, linguistic duality refers to recognizing the fancophone community, with a hospital like Montfort Hospital in Ottawa or the Vitalité Health Network in New Brunswick.
Linguistic duality can also be administrative. It is not, strictly speaking, about bilingualism.