Ind. Code § 8-1-2-11
Every public utility engaged, directly or indirectly, in any other or subsidiary business shall, if ordered by the commission, keep and render separately to the commission, in like manner and form, the accounts of all such business, in which case all the provisions of this chapter shall apply with like force and effect to the books, accounts, papers, and records of such other business; provided, every public utility may, with consent of the commission and the proper local authorities, furnish to all patrons or persons applying therefor any service, product, or commodity which it creates as a necessary incident and subsidiary to its main or primary business. No such consent shall be granted except as provided in section 86 of this chapter, and every such subsidiary business shall be subject to all the provisions of this chapter.
IC 8-1-2-11