(1) An eligible employee who elects to participate in an optional retirement program established under this part will be ineligible to participate in the retirement system during such period as the employee is employed by a state-supported institution of higher education.
(2) While participating in an optional retirement program, such member's accumulated contributions, if any, and creditable service in the retirement system shall remain unchanged as of the date of election of an optional retirement program under this part.
(3) Interest shall continue to be credited to the employee's accumulated contributions in the retirement system.
(4) In the event that a participant in an optional retirement program assumes or returns to a position in a public school where an optional retirement program or a local retirement fund is not available, the participant shall at that time begin or resume participating in the retirement system.