Notwithstanding any general or special law, rule or regulation to the contrary, the retirement board of the City of Boston shall credit Michael Sullivan with creditable service for the period of December 3, 2000 to October 31, 2005, inclusive, for the purpose of determining his superannuation retirement allowance under paragraph (a) of subdivision (2) of section 5 of chapter 32 of the General Laws. During this time, Michael Sullivan served as a full time sworn Police Officer for the City of Warwick, Rhode Island Police Department. Before the date that any retirement allowance becomes effective for Michael Sullivan, he shall pay into the annuity savings fund of the retirement system of the City of Boston Retirement Board in one sum or installments, upon such terms and conditions as the board may prescribe, an amount equal to that which would have been withheld as regular deductions from his regular compensation for such previous service.