Cal. Health and Safety Code § 13965

If the civil service commission or body performing employee relations functions for a district finds that a person has been employed by a city or another district which has, or any portion of which has, been annexed to, included within, or contracts with, the district for all fire protection, rescue, or emergency medical services, in a position classification the duties of which and qualifications for which are substantially the same as those of any position classification in the district, at the request of the district board, the civil service commission or other body may certify, without examination, that person as eligible to hold that district position classification or any lower position classification for which the person is qualified and which would not result in a lower level of salary than was received by the person immediately before the annexation, inclusion, or contract. If a person is employed by the district after certification without examination by the civil service commission or other body because of his or her employment in a position classification of similar duties by a city or district, all time employed in that city or district shall be considered as time employed by the district, to determine seniority rights and salary rates.