This Part applies to every public utility, as defined in Section 3-105 of the Act (Ill. Rev. Stat. 1985, ch. 111⅔, par. 3-105), under the jurisdiction of the Commission, and every telecommunications carrier subject to Article IX of the Act (Ill. Rev. Stat. 1985, ch. 111⅔, pars. 9-101 through 9-252).