Section 12. The department, with the concurrence of the county commissioners, may discontinue as a state highway any way or section of way laid out and constructed under the provisions of section five by filing in the office of the county commissioners for the county and in the office of the clerk of the town in which such way is situated a certified copy of a plan showing the way so discontinued and a certificate that it has discontinued such way; and thereafter the way or section of way so discontinued shall be a town way. Said department may also abandon any land or rights in land which may have been taken or acquired by it by filing in the office of the county commissioners for the county and in the office of the clerk of the town in which such land is situated a certified copy of a plan showing the land so abandoned and a certificate that it has abandoned such land, and by filing for record in the registry of deeds for the county or district in which the land lies a description and plan of the land so abandoned; and said abandonment shall revest the title to the land or rights abandoned in the persons in whom it was vested at the time of the taking, or their heirs and assigns.