SECTION 59.
Section 23 of said chapter 32B, as so appearing, is hereby amended by striking out, in lines 40 and 41, the words "at 3 year intervals from the date of transfer of subscribers to the commission" and inserting in place thereof the following words:- after an initial 3-year period from the date of transfer of subscribers to the commission, at whole-year intervals; provided, however, that such whole-year intervals shall not be less than 2 years in length as determined by the written agreement established in subsection (c) of section 21.