If eligible under federal law, a political subdivision may extend the benefits of the uniform group insurance program under this chapter to its permanent employees, subject to minimum requirements established by the board and a minimum period of participation of sixty months. If the political subdivision withdraws from participation in the uniform group insurance program, before completing sixty months of participation, unless federal or state laws or rules are modified or interpreted in a way that makes participation by the political subdivision in the uniform group insurance program no longer allowable or appropriate, the political subdivision shall make payment to the board in an amount equal to any expenses incurred in the uniform group insurance program that exceed income received on behalf of the political subdivision’s employees as determined under rules adopted by the board. The Garrison Diversion Conservancy District, and district health units required to participate in the public employees retirement system under section 54-52-02, shall participate in the uniform group insurance program under the same terms and conditions as state agencies. A retiree who has accepted a retirement allowance from a participating political subdivision’s retirement plan may elect to participate in the uniform group under this chapter without meeting minimum requirements at age sixty-five, when the employee’s spouse reaches age sixty-five, upon the receipt of a benefit,    when the political subdivision joins the uniform group insurance plan if the retiree was a member of the former plan, or when the spouse terminates employment. If a retiree or surviving spouse does not elect to participate at the times specified in this section, the retiree or surviving spouse must meet the minimum requirements established by the board. Each retiree or surviving spouse shall pay directly to the board the premiums in effect for the coverage then being provided. The board may require documentation that the retiree has accepted a retirement allowance from an eligible retirement plan other than the public employees retirement system.