Every improvement area established prior to January 1, 1990, pursuant to the Parking and Business Improvement Area Law of 1979 (former Part 6 (commencing with Section 36500) of this division) is hereby declared valid and effective and is unaffected by the repeal of that law, but is subject to Chapters 3 (commencing with Section 36530), 4 (commencing with Section 36540), and 5 (commencing with Section 36550) of this part rather than any provision of prior law.