Chapter 1, Laws of 1931, shall not be deemed or construed to repeal or affect any existing act, or any part thereof, relating to the construction, operation and maintenance of public utilities by irrigation or water-sewer districts or other municipal corporations, but shall be supplemental thereto and concurrent therewith. No public utility district created hereunder shall include therein any municipal corporation, or any part thereof, where such municipal corporation already owns or operates all the utilities herein authorized: PROVIDED, that in case it does not own or operate all such utilities it may be included within such public utility district for the purpose of establishing or operating therein such utilities as it does not own or operate: PROVIDED, FURTHER, That no property situated within any irrigation or water-sewer districts or other municipal corporations shall ever be taxed or assessed to pay for any utility, or part thereof, of like character to any utility, owned or operated by such irrigation or water districts or other municipal corporations.