Does the attorney work product rule apply to expert opinions?

Pen. Code, 1054.6 ["Neither the defendant nor the prosecuting attorney is required to disclose any materials or information which are work product as defined in ... the Code of Civil Procedure"].) "The opinions of experts who have not been designated as trial witnesses are protected by the attorney work product rule. [Citation.] Their identity also remains privileged until they are designated as trial witnesses." ( Hernandez v. Superior Court (2003) 112 Cal.App.4th 285, 297, 4 Cal.Rptr.3d 883.)