Any electric powerplant or major fuel-burning installation issued an order pursuant to section 792(c) of title 15 that is pending on the effective date of this chapter shall, notwithstanding the provisions of such section 792(c) or any other provision of this chapter, be subject to the provisions of this chapter as if it were a new electric powerplant or new major fuel-burning installation, as the case may be, except that if such order became final before such date, the provisions of subchapter II of this chapter shall not apply to such powerplant or installation.