The concepts of NAL dealings/lien de dépendance may have evolved since Swiss Bank
After discussing the concept of parties dealing at arm’s length and its judicial treatment , including the concepts of acting in concert, and then of captive interest, that surfaced in the two levels of decision in the Swiss Bank case, and how subsequent courts dealt with these concepts, the authors conclude:
[T]he interpretation of Swiss Bank by later jurisprudence has given different meaning to the determination of whether parties are dealing at arm's length than what was intended by the Exchequer Court, or even the Supreme Court. Justice Thurlow looked to see whether A and B acted in concert without separate interests to test whether they were NAL with C, not with each other, but the CRA and most courts seem only interested in applying the acting in concert test bilaterally. The SCC decision in Swiss Bank is predominantly cited for the test it rejected, and almost never for the test it put forward (i.e., captive interest). This has been coupled with a deemphasis of the word "dealing" in the arm's length determination, with a resolute focus on what the relationship is between the parties. However, once a refrain is repeated often enough it tends to take on a life of its own, meaning that even with tenuous origins, the "acting in concert" test as it currently stands is likely here to stay.
Neal Armstrong. Summary of Matias Milet and Emily Gilmour, “A Discordant Jurisprudence: What does it Mean to be ‘Acting In Concert’?,” International Tax (Wolters Kluwer CCH), No. 118, June 2021, pp. 1-7 under s. 251(1)(c).