What fun. This is a tech that is rapidly working downwards and there are several hobby groups as well as cheap commercial toys working in this area. So this looks like a severe underestimate:-
And some have forecast that by the year 2018 there will be “more than 15,000 [unmanned aircraft systems] in service in the U.S., with a total of almost 30,000 deployed worldwide.”
There are signs all along I-10 between Tucson and Phoenix that speed can be tracked by air surveillance. If you look along the freeway, you can see lines painted on the shoulder about every quarter mile to help track your spurred from above. I'm pretty sure these used to be manned, but would not put it passed them to use drones.
I once wrote a fictional short story about something similar back when I was in school in the mid '80s. It's kinda surreal to actually see it happen.
Also heard architectural surveyors using drones to inspect an old viaduct. saved them weeks, and no need for expensive scaffolding.
http://www.bbc.co.uk/news/technology-16367042