California Code, Government Code - GOV § 22156

(a) A division of the State Teachers' Retirement Plan is hereby authorized by the Legislature to provide Medicare coverage for employees of a public agency, as defined in Section 22009.03, upon the request of the public agency.

(b) The division authorized by subdivision (a) shall be conducted pursuant to this article.

(c) A member of the State Teachers' Retirement Plan on whose behalf a request is made pursuant to subdivision (a) may elect to be covered by Medicare, pursuant to Section 218 of the federal Social Security Act (42 U.S. C. Sec. 418), and applicable federal regulations if all of the following apply:

(d) The public agency shall immediately make an application pursuant to Chapter 2 (commencing with Section 22200) of this part for Medicare coverage for those members who have elected to receive Medicare coverage.

(e) The effective date of the coverage may be retroactive, but not earlier than the last day of the sixth calendar year preceding the year in which the agreement or modifications, as the case may be, is submitted to the Commissioner of Social Security.