Any grantor who, prior to the effective date of this Act, shall have conveyed land abutting a town or private way, county road or highway, with the intent to reserve his title in such road or way, but who shall not have expressly reserved his title thereto by specific reference as required in section 461, or any person who claims title to any road or way, or discontinued portion thereof, by, through or under, or as the heir, successor, executor, administrator or assign of any such grantor, may preserve his title or claim by filing the notice provided in section 463 in the registry of deeds for the county in which the road or way is located, within 2 years after the effective date of this Act. In any action concerning title to a road or way, or discontinued portion thereof, the burden of proof in establishing the grantor's intent to reserve such title shall be on said grantor or those claiming by, through or under him.   [PL 1973, c. 505 (NEW).]