(a)
Upon the expiration of the leave of absence granted pursuant to Section 89510 the employee to whom the leave of absence was granted is entitled to reinstatement in the position he held at the time the leave of absence was granted him, if the position is still in existence, or to any other comparable existing vacant position for which he is qualified.
(b)
If the provisions of this section are in conflict with the provisions of a memorandum of understanding reached pursuant to Chapter 12 (commencing with Section 3560) of Division 4 of Title 1 of the Government Code, the memorandum of understanding shall be controlling without further legislative action, except that if such provisions of a memorandum of understanding require the expenditure of funds, the provisions shall not become effective unless approved by the Legislature in the annual Budget Act.