(a) For all purposes under this part, the following group of employees shall constitute a separate coverage group: civilian employees of National Guard units of the state who are employed pursuant to Section 90 of the National Defense Act of June 3, 1916 (32 U.S.C. Sec. 42), and paid from funds allotted to those units by the Department of Defense.
(b) The Adjutant General may enter into an agreement with the board pursuant to Section 22203 for the purpose of obtaining coverage under the federal system for these employees.