Let's just say they really give a **** about provincial rights.
Federations, by definition, divide powers and certain powers, such as international transportation networks, are the exclusive domain of the federal government.
When provincial powers may infringe on federal domain the doctrine of Federal Paramountcy applies:
The Doctrine of Federal Paramountcy[20]
Federal paramountcy protects federal powers from provincial intrusion. While both the provincial and the federal governments may legislate on a common matter, the federal legislation will prevail in the event of a conflict. [21] There are two types of potential conflict, the first is where “it is impossible to comply with both laws” and the second occurs where “to apply the provincial law would frustrate the purpose of the federal law.”[22] Courts have found federal paramountcy preferable over the application of the interjurisdictional immunity doctrine as it will only limit the provincial legislation to the extent that it conflicts with federal jurisdiction and no further.[23]
IOW - even if the court affirmed the provinces roles in regulating waterways this power could NOT be used to frustrate a federal law.