Section 51. The department of telecommunications and energy, upon petition of the commission and after due notice to the railroad corporation, shall hear the parties, and, if of the opinion that said petition should be granted, shall make a decree describing the place, time and manner of constructing such crossing, and how much, if any, of the work made necessary by such crossing shall be done by the corporation; and thereafter the commission may lay out, construct and maintain such boulevard across the railroad in accordance with the terms of said decree.