California Code, Revenue and Taxation Code - RTC § 10789

(a) Any vehicle purchased with federal funds under the authority of paragraph (2) of subsection (b) of Section 1612 of Title 49 of the United States Code or Chapter 35 (commencing with Section 3000  1) of Title 42 of the United States Code for the purpose of providing specialized transportation services to senior citizens and handicapped persons by public and private nonprofit operators of specialized transportation services, including a consolidated transportation service agency designated pursuant to Section 15975 of the Government Code.

(b) Any vehicle operated solely for the purpose of providing specialized transportation services to senior citizens and persons with disabilities, by a nonprofit, public benefit consolidated transportation service agency designated under Section 15975 of the Government Code. The exemption provided by this subdivision shall not apply to more than 600 vehicles at any given time.