No transfer to the state of North Dakota or any of its political subdivisions of property for highway purposes shall be deemed to include any interest greater than an easement, and where any greater estate shall have been so transferred, the same is hereby reconveyed to the owner from which such land was originally taken, or to the heirs, executors, administrators, or assigns of such owner. Such reconveyance shall be subject to any existing contracts or agreements covering such property, and all rights and benefits thereof shall accrue to the grantee.