Section 92(10) of the Constitution Act, 1867
[...]
Declaratory power under section 92(10)(c)
In general terms, works declared by the Parliament of Canada to be "for the general Advantage of Canada" or "for the Advantage of Two or more of the Provinces" tend to be part of the national
infrastructure.
Whenever parliament invokes the power, it gains not only jurisdiction over the work but also any necessarily incidental operations. In
Ontario Hydro v. Ontario (1993), such a declaration had been made with respect to Ontario Hydro's nuclear plant. The Supreme Court held that that declaration gave Parliament the authority to regulate the work "as a going concern" which included jurisdiction over workers at the plant and their labour unions.
The declaration must be made by the passing of legislation, but in addition to declaring specific works, whole classes of work can be defined as being "for the general advantage of Canada" by default; the
Atomic Energy Control Act, for example, deemed all nuclear power plants to fall into this category. From 1867 to 1961 there were 470 uses of the declaratory power, of which 84% related to railways.
As of 2006, the declaratory power has been invoked at least 422 times,
[6] but not since 1961,
[7] and of which 64% was related to railways.[...]