4. An affiliated real estate broker’s certificate, provided for in paragraph 3 of section 1, may be issued only to a natural person holding a broker’s permit issued by the Superintendent of Real Estate Brokerage under the Real Estate Brokerage Act (chapter C-73) who was employed by a broker or was authorized to act on behalf of a broker on 20 June 1991. A holder of that certificate may use the title of affiliated real estate broker but may engage in a brokerage transaction referred to in section 1 of the Act only if he is employed by the holder of a chartered real estate broker’s certificate or by a multidisciplinary firm holding a certificate provided for in any of paragraphs 5 to 10 of section 1 of the Regulation respecting multidisciplinary firms (O.C. 1020-91 [I-15.1, r. 0.3]), and issued under the Act respecting market intermediaries (chapter I-15.1), or if he is authorized to act on behalf of a holder of such a certificate. A holder of that certificate may not employ the holder of a real estate broker’s or agent’s certificate or authorize such a person to act on his behalf.