A US enterprise arguably can acquire a Canadian services PE by providing services only to related Canadian enterprises

The US Joint Committee on Taxation stated that the services PE concept in the Canada-U.S. Treaty “only applies to services provided by the enterprise to third parties and not to services provided to that enterprise (i.e. inter-company services)." In 2009-0319441C6, CRA rejected the proposition that this means that there can be no services PE where services are only rendered between related parties. The CRA position might correct on the basis that the Joint Committee report was merely indicating “that services provided to the nonresident enterprise by its affiliates do not result in a PE to the enterprise to whom the services are provided,” as contrasted to excluding services provided by a non-resident enterprise to related parties.

Neal Armstrong. Summary of Abraham Leitner and Peter Glicklich, "Uncertainty Remains Under the Services PE Provision in the U.S.-Canada Income Tax Treaty," Tax Management International Journal, 2015, p. 784 under Treaties – Art. 5.