What is the test for federal paramountcy?

As recently discussed in Canadian Western Bank v. Alberta, [2007] 2 S.C.R. 3, 2007 SCC 22, under the paramountcy doctrine, “when the operational effects of provincial legislation are incompatible with federal legislation, the federal legislation must prevail and the provincial legislation is rendered inoperative to the extent of the incompatibility”: para. 69. Further, for the doctrine to apply, “the onus is on the party relying on the doctrine of federal paramountcy to demonstrate that the federal and provincial laws are in fact incompatible by establishing either that it is impossible to comply with both laws or that to apply the provincial law would frustrate the purpose of the federal law”: para. 75.