Beginning July 1, 1996, if a municipality selling water to persons or public or private entities outside its corporate limits has not implemented an enterprise accounting system to account for the cost of water supply, treatment and delivery to the point of delivery to the purchaser's water system, it shall be liable to the purchaser for the reasonable expenses of such an accounting exceeding the expense which the purchaser would have incurred using an enterprise accounting system.
Okla. Stat. tit. 11, § 37-119a