The state reserves to itself the right, acting in conjunction with any adjoining state or municipality thereof, to acquire any bridge constructed by any such company at the following times and upon the following terms:

a. At the expiration of five years after the opening of any bridge for public use, for the total costs thereof of whatever nature and upon assumption of all obligations or liabilities of the bridge company, for the construction of the bridge, with the approaches thereto and appurtenances thereof, plus fifteen per cent of the cost;

b. At any time thereafter, at such total cost and upon assumption of such obligations or liabilities, plus fifteen per cent of the cost, less two per cent per annum of the total cost for each year after the expiration of five years from the date of the opening of the bridge for public use.

Every company organized under this article consents to the acquisition by the state pursuant to this section of any bridge constructed by the company.