§ 1254. Use of special equalization ratios. Notwithstanding the provisions of any general or special law, the ratios established in accordance with the provisions of this article shall be used in calculating average full valuation of taxable real estate of a city in computing and applying the limitation on the amount to be raised by tax on real estate pursuant to section ten of article eight of the constitution and the limitation on local indebtedness pursuant to section four of article eight of the constitution for the fiscal year of such city for which such assessments are used in computing such limitations.