This is a good article that explains how drones might be used and the challenges that exist today with using the technology. But mission parameters for drones are only going to expand and there will be new technological developments that make their use and limited payload not as much of an issue.
You can be certain that it will lead to efficiencies in staffing and operating the railroad. But it is hard today to replace the human eye and some of the more sophisticated technology that weighs too much for the payloads of today's drones.
