This subsection applies to an election to participate in the program made on or before June 30, 2017. Except as otherwise provided in this section, an election to participate in the program is a waiver of all rights and benefits provided by the retirement or pension system in which the participating employee was a member on the effective date of the election. For the purpose of determining eligibility for immediate vested rights or benefits in a retirement system or pension system, an eligible employee who is a member of that State system when the employee elects to participate in the program is deemed to have separated from employment on the effective date of the election. The Board of Trustees may only compute retirement system or pension system benefits on the basis of years of creditable service as a member of that State system. This paragraph applies only to a participating employee whose last employer prior to joining the program was a participating employer that does not participate in the employer pick–up program as defined in § 414(h)(2) of the Internal Revenue Code. A participating employee may withdraw any accumulated contributions in the annuity savings fund on or after the effective date of the participating employee’s election to join the program. If a participating employee withdraws the accumulated contributions, the participating employee forfeits any right to a benefit in the State system from which the accumulated contributions were withdrawn. A participating employee is ineligible for membership in a retirement system or pension system while the participating employee is employed in any eligible position by any employing institution. A participating employee who is subsequently appointed, promoted, or transferred to another position that is eligible for membership in a State system but is not eligible for participation in the program shall participate in a State system with respect to that position as a condition of employment.