Section 70. A railroad corporation may acquire, hold, vote, sell and negotiate the stock and securities of terminal companies organized under the laws of the commonwealth, and of express companies operating in whole or in part on its lines, and may guarantee the bonds of such companies. Such a corporation may acquire, hold, vote, sell and negotiate stock in subsidiary corporations organized under the laws of the commonwealth to operate aircraft and/or motor vehicles not running on rails or tracks for the transportation of passengers and/or freight.