(b)with the previous sanction of [the Officer Commanding in-Chief, the Command and] [Inserted by Act 24 of 1936, s.18] the [State Government concerned] [Substituted by the A.O. 1937, for "L.G."], enter into an agreement with any other local authority regarding the levy of any tax or toll whereby the said tax or toll respectively leviable by the [Board and such other local authority] [Substituted by Act 24 of 1936, s.18 for "said authorities"] may be levied together instead of separately within the limits of the aggregate area comprising the areas subject to the control of the [Board and such other local authority] [Substituted by Act 24 of 1936, s.18 for "said authorities"].