Cal. Welf. & Inst. Code § 4122

The State Department of State Hospitals, when it deems it necessary, may, under conditions prescribed by the director, transfer any patients of a state institution under its jurisdiction to another institution. Transfers of patients of state hospitals shall be made in accordance with the provisions of Section 7300.

The expense of any transfer shall be paid from the moneys available by law for the support of the department or for the support of the institution from which the patient is transferred. Liability for the care, support, and maintenance of a patient so transferred in the institution to which he or she has been transferred shall be the same as if he or she had originally been committed to the institution. The State Department of State Hospitals shall present to the county, not more frequently than monthly, a claim for the amount due the state for care, support, and maintenance of any such patients and which the county shall process and pay pursuant to the provisions of Chapter 4 (commencing with Section 29700) of Division 3 of Title 3 of the Government Code.