Yes, but that grandfather clause does not call into question the principle that all voters are equal. It simply forces us to add seats to ensure that there is voter equality. As for the other clause—the one that prevents there being fewer MPs than senators—it is in the Constitution. If we're saying that a province has guaranteed representation—maybe forever; I really don't know—that is definitely something that could be challenged because of the voter equality principle, which is a constitutional principle.
On October 18th, 2011. See this statement in context.