If such bridge is altered, rebuilt, improved or repaired under sections fifty-nine to sixty-four, inclusive, of chapter one hundred and fifty-nine, the cost of construction of the tracks upon and over such temporary location shall be reckoned as a part of the charges and expenses of the alteration, improvement or repair of the crossing, to be apportioned by the special commission as provided thereunder.
Mass. Gen. Laws ch. 161, § 76