(a) Section 27606 does not apply to vehicles owned or used by persons licensed pursuant to Article 3.1 (commencing with Section 7540) or Article 3.2 (commencing with Section 7544) of Chapter 11.5 of, or Chapter 11.6 (commencing with Section 7590) of, Division 3 of the Business and Professions Code in the performance of their duties under those provisions.
(b) This section does not authorize those persons described in subdivision (a) to equip a vehicle with a light bar if prohibited by other provisions of existing law or regulation.