Section 20. Notwithstanding any other provision of general or special law, a city or town may own a unit of a condominium under this chapter, participate in the organization of unit owners and be liable for its share of the common expenses of the condominium. Said city or town may either purchase a unit of a condominium or, if the city or town intends to become the owner of such a unit and use the same for municipal purposes, it may contract for the creation of a condominium and for the advancement to the city or town of the acquisition costs allocable to all other units therein. It may acquire land therefor or devote thereto land already owned by it, construct, reconstruct or remodel a building thereon subject however to the provisions of chapter one hundred and forty-nine notwithstanding that said building is not intended solely for municipal uses, and execute and record a master deed submitting such land and building to the provisions of this chapter. Upon the completion of the said construction, reconstruction or remodelling it may convey to such other parties to said contract such units as have been paid for in the proportion of the aggregate cost allocable to their stipulated units. The authority contained in this section shall be exercised, in the case of the city of Boston, by its public facilities commission, in the case of a city having a Plan E charter, by the affirmative vote of a majority of its city council, in the case of any other city, by its city council subject to the provisions of its city charter, and in the case of a town, by its town meeting.