Government Code § 26508
ARTICLE 1. Duties as Public Prosecutor
A district attorney, with the concurrence of the district attorney of another county and the boards of supervisors of both affected counties, may provide to the district attorney of such other county legal or investigative services, or both, pertaining to the prosecution of a civil cause of action in the other county by the district attorney of that county. The county provided with such services shall compensate the county providing the services at a rate which is mutually agreeable to the counties as parties to the agreement.