Section 10A. On or before June tenth, in each year in which an equalization is to be established, the commissioner shall hold a public hearing on the proposed equalized valuations. He shall send written notice thereof, together with a copy of the proposed equalized valuations, to the assessors of each city and town on or before June first of such year. The commissioner may, on the basis of any new information furnished to him at such hearing or otherwise, change the proposed equalized valuation of any city or town. Notice of any change shall be sent to the assessors of such city or town on or before July twentieth next following.