Any municipality having a population in excess of twenty-five thousand and less than two hundred fifty thousand owning and operating its electric power plant, waterworks, motor coach transportation, and sewerage system, may construct, maintain, extend, rehabilitate, enlarge or improve any municipally owned public utility either within or without its boundaries.  In addition the municipality may consolidate and unite any non-revenue bearing utility with one or more revenue bearing public utilities, which, when so united and consolidated, shall be one unit and shall be considered and treated as a single revenue bearing utility.