The City Council or other board or agency of the City operating the electric plant may charge the City and all departments, agencies, instrumentalities, officers, or employers thereof for any electric service furnished to them, at the rate applicable to other customers taking service under similar conditions and the revenues so derived from any such service shall be treated as all other revenues of the electric plant. Notwithstanding the foregoing, special contracts for electric services may be entered into with another department, agency, or instrumentality of the City, provided that the Public Utility Commission first reviews and approves the contract pursuant to the provisions of 30 V.S.A. § 229.