(1) If the system is operated as a single unit, by a joint board or by 1 public corporation as agent for all, the operating board or agency shall provide for the payment of the necessary amounts into the operation and maintenance fund and into the bond and interest redemption fund for all bonds secured by the revenues of the entire system. The public corporations may, by contract, provide for the joint holding and management of other revenues or for their apportionment and deposit into separate bond and interest redemption funds for bonds, severally issued or assumed and into separate depreciation, contingent, and surplus funds. Unless otherwise provided by the contract, those revenues shall be divided and paid quarterly or more often into their respective treasuries and set apart by each into the appropriate funds. Unless otherwise provided by the contract, each public corporation shall have control of the construction of extensions and improvements to the system within its boundaries, and shall be entitled to its proportion of the contingent and surplus funds for that purpose.

  (2) The contracts described in subsection (1) are not subject to the revised municipal finance act, 2001 PA 34, MCL 141.2101 to 141.2821.