135.4. If a balance of the surplus amount referred to in the first paragraph of section 134 remains after the reductions made mandatory pursuant to section 135.2, all or part of the surplus may be utilized to reduce proportionately each of the amortization amounts remaining to be paid to amortize one or more unfunded actuarial liabilities referred to in section 135.3 or to shorten the amortization period of such unfunded actuarial liabilities, without, in the latter case, increasing the amounts remaining to be paid. In the case of a plan referred to in paragraphs 2 to 6 of section 135.1, such a utilization may be authorized only if the city and the employees’ associations representing the majority of the members of the plan agree thereto in writing. A copy of every agreement must be transmitted to the Régie together with the report on the actuarial valuation outlining the result of the agreement.