Section 92(10) of the Constitution Act, 1867, also known as the works and undertakings power, grants the provincial legislatures of Canada the authority to legislate on:
Section 92(10)(a) and (b) grants federal jurisdiction over modes of interprovincial and international transportation and communication, leaving intraprovincial transportation and communication to the provinces. Section 92(10)(c), however, applies to works of all types. The Parliament of Canada exercises authority over these three matters under section 91(29), which states:
Section 92(10) of the Constitution Act, 1867 Wikipedia
The Judicial Committee of the Privy Council held that:"These works are physical things not services."
"'Undertaking' is not a physical thing but is an arrangement under which of course physical things are used."
A work or undertaking will be under government control under section 69(10) where it is connecting the province with something outside of the province. This does not mean that physical connection is sufficient. An undertaking will be considered "connecting" where business operations extend beyond the provincial border, or has a close operational relationship with an inter-provincial undertaking
The reference to "Telegraphs" has been held to include telephones and radio broadcasting. In the latter case, radio broadcasting was held to have no provincial dimension, and was therefore exclusively a federal matter. That has since been extended to include television and cable television.
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, but not since 1961, and of which 64% was related to railways.