Section 17. Exchange or sale of railroad stock and bonds

The railroad
  commissioners or officers of a municipal corporation, having the  lawful
  charge  and control of any railroad stock or bonds, for or in payment of
  which the bonds of such municipal corporation have been lawfully  issued
  in  aid of such railroad corporation, may exchange the stock or bonds of
  such railroad corporation for and in payment of such bonds, or  the  new
  substituted  bonds of such municipal corporation, when such exchange can
  be made for not less than the par value of the stocks or bonds  so  held
  by them. If they can not make such exchange they may sell such stocks or
  bonds  at  not  less than par; but they may, on the application and with
  the approval of the governing board of the municipal corporation  owning
  such  stock  or bonds, exchange, sell or dispose of such stock or bonds,
  at the best price and upon the best terms obtainable, for the  municipal
  corporation  they  represent,  and  shall  execute  to the purchaser the
  necessary transfers therefor. All moneys received for any stock or bonds
  shall only be applied to the payment and extinguishment of the bonds  of
  the  municipal corporation, lawfully issued in aid of any such railroad,
  or  substituted  therefor;  except  that  if  the  bonds  so  issued  or
  substituted  have all been paid, or the moneys so realized shall be more
  than sufficient to pay them in full, and all the costs and  expenses  of
  the sale, such proceeds or balance thereof shall be paid by the officers
  making  the sale, to the supervisor of the town, or the treasurer of the
  municipal corporation, and applied to such lawful uses as the  governing
  board  of  the  municipal corporation, entitled to the same, may direct.
  The provisions of this section shall apply to all such commissioners  or
  officers of a municipal corporation elected or appointed or acting under
  the  provisions  of  any special act, and the authority hereby conferred
  shall not be limited by the provisions of any such special act.