In establishing rates, depreciation expense will be permitted only against investor-supplied plant, as determined by the Commission. Rebuttable Presumption of Contributed Plant. An applicant under Public Utilities Article, §5-204, Annotated Code of Maryland, shall be rebuttably presumed to consist of entirely contributed plant for which the total cost and investment either has been or will be recovered. Proof of actual investment by investors, organizers, and owners of an applicant may be established by the presentation to the Commission of the books, records, accounts, audited financial statements, and other pertinent documents and testimony of all persons, corporations, and business entities (except regulated financial institutions engaged in the financing, construction, and the operation of the applicants for the period of financing and construction).