Any mortgagee or trustee of the tenant's interest in such lands, or any part thereof, whether he be in possession of the lands or not, may, within twelve months after execution executed, pay the rent and all arrears, with interest and costs, or file a bill in equity for relief against such forfeiture; and thereupon may be relieved against it, on the same terms and conditions as the tenant of such lands or tenements would be entitled to.