Section 70. Notwithstanding the provisions of sections thirty-one and fifty-three, any city or town may, by vote of its town meeting, town council or city council authorize the collector, treasurer or other department head, with the approval of the selectmen, town manager or mayor, to enter into contracts to identify and pursue federal government reimbursements for, or other revenues or available resources that may be generated by, programs or activities being carried out by the municipality, and to provide that payments for services under such contracts may be made from the reimbursements or revenues recovered as a result of the services performed without appropriation of such revenues. The provision of this section shall not apply to reimbursements, revenues or resources that may be available from the medical care and assistance program administered by the commonwealth pursuant to chapter one hundred and eighteen E.