Section 7A. Any certificate of public convenience and necessity granted by the department pursuant to section seven and chapter three hundred and seventy-eight of the acts of nineteen hundred and forty-seven and any license or permit granted pursuant to sections one, three and eleven A, may be assigned and transferred in whole or in part, with the approval and consent of the department, after a public hearing, at which hearing it shall be established to the satisfaction of the department that the proposed transfer and assignment are consistent with the public interest, that public convenience and necessity require it, and that the transferee is fit, willing and able properly to conduct the operation or business authorized by said certificate, provided, however, that no certificate, license or permit shall be transferred except in connection with the bona fide sale to the transferee of the business of the transferor theretofore conducted in connection with the certificate, permit and license or any part thereof sought to be transferred. Notice of such public hearing shall be given to the holders of licenses issued under section eleven A in the city or town into which said change is sought to be made, and to holders of certificates issued under section seven and doing business in such city or town.

No person, firm, trust or corporation subject to the jurisdiction of the department shall hereafter purchase, acquire, take or hold, directly or indirectly, any part of the capital stock of any carrier subject to the provisions of this chapter, nor shall any person, any associated group of persons or any firm, trust or corporation, who or which is not subject to the jurisdiction of the department, acquire, take or hold, directly or indirectly, more than fifty per cent of the voting capital stock of a carrier subject to this chapter, unless authorized so to do by the department. No consent shall be given by the department to the acquisition as aforesaid unless it shall have been shown that such acquisition is consistent with the public interest, and if such consent is given in whole or in part the department may impose such terms and conditions as it shall deem to be in the public interest. Nothing herein contained shall be construed to prevent the holding of any stock heretofore lawfully acquired by a person, firm, trust or corporation, or, upon the surrender or exchange of said stock pursuant to an agreement of consolidation or merger or a reorganization plan, to prevent the purchase, acquisition, taking or holding of the voting capital stock of the new corporation organized pursuant to such agreement or plan to take over the property of any corporation whose stock has been thus surrendered or exchanged, or to prevent the purchase, acquisition, taking or holding of any further issue of stock, provided such further issue does not increase the proportion of voting capital stock held by such person, firm, trust or corporation. For the purposes of this section only the word ''carrier'' shall be construed to include any person, partnership, corporation or association owning or operating a motor vehicle actually used for the transportation of school children under a contract with a municipality or municipal board or for the transportation of school children in a school bus as defined in section one of chapter ninety to or from events of public interest. No person or associated group of persons owning or controlling more than fifty per cent of the stock of any corporate common carrier subject to the jurisdiction of the department under this chapter shall engage in business as a carrier as so defined without the consent of the department.