16. A service centre or an educational institution that avails itself of the first paragraph of section 15 is not authorized to negotiate a contract with the carrier that would increase the total number of buses and minibuses it requires from the carrier in relation to the preceding school year, except:(1) where the contract is for the transportation of handicapped students or for the transportation of students with social maladjustments and learning disabilities and that transportation must be provided by means of a bus or a minibus adapted to such transportation; or
(2) where the contract provides for the addition of 1 vehicle only and has been previously offered on the same conditions to any carrier whose contract for a bus or a minibus was cancelled during the preceding school year or was not renewed for a reason not related to the quality of service.