Notwithstanding the provisions of any general or specific law to the contrary any person who is receiving a retirement allowance pursuant to sections 1 to 28 of chapter 32 of the general laws and whose retirement allowance was calculated pursuant to Option (c) of chapter 12 of said chapter 32, upon adoption of this section by the appropriate retirement board, shall be entitled to a recalculation of his retirement allowance based on an updated mortality table adopted pursuant to section 336 of chapter 149 of the Acts of 2004.  Prior to adoption of this section, a retirement system shall conduct an actuarial study to determine the costs and liabilities of recalculating option (c) retirement allowances.  Upon adoption of this section, a retirement system shall notify any eligible persons of this option and such persons shall request, in writing, within 180 days of such notification, that a recalculation of his retirement allowance be made.  Such recalculation may be made retroactively to any date on or after the acceptance of this act, provided that any system responsible for payment of the retirement allowance shall pay to such person, in one lump sum, the difference between the amount paid and the amount due under the recalculated retirement allowance.