Its highly unlikely that you would ever come across this equipment as long as you fly in safe areas. The public using this stuff is going to affect very few people. Its mega expensive.
As I understand it they can do only two things, make it land or send it out of the area on a RTH. It is a crime to bring a drone down in any way other than a safe landing as it is treated as an aircraft under the aviation rules. This may change in time of course.
This doesn't tell everything, last I know they can control SOME drones, but with recent DJI machines they can only prevent communications. This can even be seen in the video on the page you linked (in their interface for a Solo there are several actions available like "land in specified area", but for the encrypted link of a Phantom 3 the only available one is "disable controller and initiate failsafe").
For non encrypted stuff like hobby gear most of existing protocols have been reverse engineered. So you know what the signal of a transmitter looks like, so you can look for one. When you found one you can read everything, display the channels and read the radio identifier. Someone can look at the channel movements and deduct what channel is what so that he knows how to fly the thing manually like you'd do after starting to transmit his own orders with your radio's identifier.
