Is there any case law that disqualifies an attorney who has represented at least one client at the same time in two separate actions?

subjects of the prior and the current representations can be demonstrated, access to confidential information by the attorney in the course of the first representation (relevant, by definition, to the second representation) is presumed and disqualification of the attorney's representation of the second client is mandatory; indeed, the disqualification extends vicariously to the entire firm. [Citations.]" (Flatt v. Superior Court (1994) 9 Cal.4th 275, 283-284.)