Notwithstanding the provisions of the general statutes, each municipal employer and each employee organization in a municipality that is required to close all nonessential municipal offices in observance of Martin Luther King Day pursuant to subsection (b) of section 7-478b shall reopen each collective bargaining agreement approved in accordance with the provisions of sections 7-467 to 7-477, inclusive, for the sole purpose of negotiating compensation or exchange of benefits, if any, for the bargaining unit members covered by such agreement for observance of Martin Luther King Day.