(a) In the event that a service award program provides for prior service contributions, each ambulance company for which the program is adopted shall identify on the list prepared pursuant to subdivision (b) of section 150.6 of this Part those participants who are entitled to one or more prior service contributions and the number of years for which each participant is entitled to such prior service contributions. Any participant who is denied a prior service contribution for one or more years may appeal to the governing board at the same time, in the same manner, and with like effect as provided in subdivision (d) of section 150.6 of this Part. Except as provided in subdivision (b) of this section, prior service contributions shall be paid to the administrator in a single lump sum in the year in which a participant is determined to be entitled to the contribution, by remitting, together with any payment required by subdivision (e) of section 150.6 of this Part, an amount equal to the sponsor's contribution on behalf of each participant credited with a year of ambulance service for the first year of the program times the number of years for which each participant is entitled to a prior service contribution indicated on the list.

(b) The governing board of the sponsor may elect to pay prior service contributions in five equal annual installments. Where such an election is made, the first annual installment shall be paid on or before May 1st of the year in which a participant is determined entitled to a prior service contribution. Each subsequent annual installment shall be paid on or before May 1st of each of the four years immediately succeeding the year in which the first installment is paid, together with interest at the rate determined pursuant to subdivision (c) of this section on the unpaid balance of the prior service contribution as of the date of such payment, provided, however, that in the event that the administrator notifies the sponsor that a participant has been determined eligible for a distribution of a service award prior to the payment of the fifth annual installment, the governing board of the sponsor shall cause payment to be made to the administrator of an unscheduled prior service contribution within 30 days of receiving such notice. The unscheduled prior service contribution shall equal the unpaid balance of the participant's prior service contribution plus interest at the rate determined pursuant to subdivision (c) of this section on such unpaid balance.

(c) On or before March 31st of each year the administrator shall determine the rate of interest to be paid on the unpaid balance of prior service contributions. The rate of interest shall equal the rate of return on program assets during the preceding calendar year. The administrator shall notify sponsors of the rate of interest by inclusion in or enclosure with the report required by subdivision (a) of section 150.12 of this Part.

(d) Notwithstanding the provisions of subdivisions (a) and (b) of this section, in the case of a service award program which was in effect at any time during calendar year 1994 and which provides for prior service contributions, ambulance companies and the governing boards of sponsors shall comply with the following procedures: