Section 3A. Any banking institution doing business in the commonwealth that is a subsidiary of a bank holding company may receive deposits, renew time deposits, close loans, service loans, and receive payments on loans and other obligations in the commonwealth as an agent for another banking institution, whether located within the commonwealth or in another state, which is a subsidiary of the same bank holding company; provided, however, that the banking institution so acting as agent pursuant to this section shall not be deemed to be a branch of the principal banking institution. A banking institution acting as such agent pursuant to this section shall not conduct any activity which it would be prohibited from conducting as a principal under any state or federal law or, as a principal, have any such agent conduct any activity which such institution would be prohibited from conducting under any state or federal law. Any such agency relationship shall be consistent with safe and sound banking practices and all applicable regulations of the commissioner. For the purposes of this section, the term ''bank holding company'' shall have the same meaning as set forth in the Bank Holding Company Act of 1956 12 USC 1841 et seq.