All persons imprisoned in the state prison, the men’s reformatory, the Providence County jail, and the jails in the several counties, on October 1, 1956 shall be deemed to be imprisoned in the adult correctional institutions in accordance with this chapter and all sentences imposed upon those persons prior to October 1, 1956, shall, insofar as the sentences shall not be inconsistent with the provisions hereof, be in full force and effect and all good conduct and industrial good conduct time and parole eligibility credits earned by those persons prior to October 1, 1956, shall be credited pursuant to the provisions of any general or special law in effect prior to October 1, 1956.