Cal. Pub. Util. Code § 12133
If a civil service system is adopted for a district during the period of a leave of absence granted under Section 395.4 of the Military and Veterans Code or similar legislation, the officer or employee shall, on the termination of his leave of absence, be restored to a position in the district's civil service system wherein he shall have the same or equivalent status as of the last working day before his leave of absence began. The officer or employee shall hold that position as if appointed thereto after examination and certification from a list of eligibles, and shall be governed thereafter by the rules and regulations of the civil service system, except that if such officer or employee had held a permanent position with the district for a period of six months continuously next preceding the beginning of his leave of absence, he shall not be subject to the six months' probation period.
Ca. Pub. Util. Code § 12133