Hi Dan,
All of the regulatory and legal issues aside, your question about how to coordinate the use of multiple "drone"/UAVs is a really serious concern. In the past, when a major event occurred, such as the Nickel Plate 765 hitting Pennsylvania's Horseshoe Curve, the only thing we had to worry about was all of the 15-year old kids, each of whom had a video camera and a tripod that they just HAD to place right next to the tracks. Can you imagine what will happen when all of those kids show up with their own "drone"/UAVs. It will be bedlam. As I noted in a previous thread, if even a small percentage of these folks are people with zero common sense, you can imagine how they might compete for the best shot....see who can get the tightest close-up of the Engineer in the cab! Hopefully, everyone can see my point. Without tight regulation, this technology could open the door for some seriously reckless behavior. It only takes one idiot.
In the past, FAA has used Temporary Flight Restrictions (TFRs) as a means of controlling/prohibiting air traffic over major events. We may well see the expanded use of TFRs in the future, to deal with "drones". Already, some municipalities are passing anti-drone legislation, to keep these things from becoming a serious nuisance.
/Kevin