What is the definition of a fiduciary duty outside of the established categories?

La Forest J addressed the characteristics of a fiduciary duty outside of the established categories in Hodgkinson v. Simms 1994 CanLII 70 (SCC), [1994] 3 S.C.R. 377 at paras. 30 and 33 as follows: … relationships in which a fiduciary obligation has been imposed are marked by the following three characteristics: (1) scope for the exercise of some discretion or power; (2) that power or discretion can be exercised unilaterally so as to effect the beneficiary's legal or practical interests; and, (3) a peculiar vulnerability to the exercise of that discretion or power…. Thus, outside the established categories, what is required is evidence of a mutual understanding that one party has relinquished its own self-interest and agreed to act solely on behalf of the other party. [emphasis added]

I agree with the applicant that the respondents have failed to plead any facts that would support a fiduciary relationship on the basis of the principles articulated in Hodgkinson v. Simms. THRG made a business decision to concentrate on servicing ATI as its main client. That left it vulnerable to ATI’s decision to terminate its business relationship. However, vulnerability based on dependence on a principal client is not, by itself, sufficient to establish a fiduciary relationship in commercial relationships. Nor is the right of ATI to unilaterally terminate its contractual relationship sufficient to establish a fiduciary relationship.