Although it's not a UCL case, Acosta v. Brown, ___ Cal.App.4th ___ (Jan. 30, 2013), is instructive. It discusses several leading UCL decisions on the economic abstention doctrine, such as Alvarado v. Selma Convalescent Hospital, 153 Cal.App.4th 1292 (2007) (discussed in this blog post), Arce v. Kaiser Foundation Health Plan, Inc., 181 Cal.App.4th 471 (2010) (discussed here), and Desert Healthcare Dist. v. PacifiCare FHP, Inc., 94 Cal.App.4th 781 (2001).
This doctrine is sometimes referred to as the "equitable abstention doctrine," but this is a misnomer. It applies only in cases involving "complex economic and/or political issues [and where] the nature of the relief sought would uncommonly burden the court." Acosta, slip op. at 12 n.7 (citing Alvarado).