If, on or after the effective date of this section, substantially all of a district water system is acquired by another public agency by any method other than a vote of the electorate of that district so authorizing, the following provisions shall apply:
(a)
All funds derived from the operation of the former district system shall be separately accounted for and used exclusively for the purposes of maintenance, operation, betterments, and bond debt service of the acquired system.
(b)
No funds derived from the former district system shall be used for any other such purpose until all debt of that former system has been paid in full or until a majority vote of the electorate of the area served by that former system has authorized such other expenditures.