When will a court order a public defender to serve as a deputy to a district attorney?

[5 Cal.App.3d 827] Before any assignments are made by the court to the public defender, it is clear he has the management and control of his deputies. While in large courts it has been an established practice for both the district attorney and the public defender to assign their deputies for service in a particular department or division, that may not be enforced by a court in advance of specific case assignments therein (Mowrer v. Superior Court (1969) 3 Cal.App.3d 223, 83 Cal.Rptr. 125).