Section 50. A company may, with the consent of the board of aldermen or the selectmen, convey in cars over its tracks snow, ice, stones, gravel, dirt, or street sweepings, taken from any street or way over or through which its tracks are located, in order to keep said street or way in proper condition for travel, or may convey to any point on its line, or deliver to any connecting line or any other such company, necessary material for use in constructing, grading, repairing or improving any street or way in any city or town, or any state highway, whether on the line of any such company or not, and may make contracts with cities, towns, the department of highways, and with other such companies for the transportation of such material.