This Part applies to any person deemed a gas corporation, electric corporation, steam corporation or waterworks corporation for the purpose of the Public Service Law, who or which is engaged in carrying on any business other than owning, operating or managing a gas plant, electric plant, steam plant or water system, respectively, provided that such person's other business is not subject to the jurisdiction of the commission and is so conducted that its operations are to be substantially kept separate and apart from the owning, operating, managing or controlling of such gas, electric or steam plant or water system, and that the ownership, operation or control of any gas, electric or steam plant or water system by such person is wholly subsidiary and incidental to the other business carried on by it and is inconsiderable in amount and not general in its character. Any such person may petition the commission for exemption from compliance with the provisions of the Public Service Law as specified in this Part.