Ala. Code § 37-4-25

For all the purposes of this chapter the commission may, in its discretion, deem and treat any utility, the property of which is operated in connection with or as a part of a general system of any other utility and all of the capital stock of which or substantially all of the capital stock of which is owned or controlled by such other utility, or by any person or persons who own or control all of the capital stock or substantially all of the capital stock of such other utility as a part of or consolidated with such owning or controlling utility or such other utility whose stock is so owned or controlled.