What is the test for establishing that a prior relationship between a client and a law firm prior to the disclosure of confidential information?

This case reflects the dilemma which arose in Moffat v. Wienstein (1996) 1996 CanLII 8009 (ON SC), 135 D.L.R. (4th) 298 (O.C.G.D.) where Grange J. observed at p. 326: " ... given the drastic nature of the remedy there should be compelling and cogent evidence which provides a sufficient connectiveness between the retainers." ... In this case based on the "evidence" filed by [the client] ... I am left to "guess" at the type of ... information that [the firm] may have been privy to in their past relationship with [the client]. I am not suggesting the client must disclose the exact specifics of the confidential information it seeks to protect, but some particulars are warranted, given the remedy sought. A party does not meet its onus of establishing the prior relationship is sufficiently related to the present retainer, merely by making the bald assertion that the past relationship has provided the solicitor with access to [confidential information]. At the very least, in order to discharge its onus, the client should describe how the solicitor gained that information and why it is related to the matter at hand."