Fake or not, could this actually be done (perhaps w/ other device than an iPhone)? If so, how?
For anything like this to work remotely, there would have to be some point where the video the screen is playing is being transmitted wirelessly that you could overpower. While I obviously don't know how those screens work, I would be very surprised if it wasn't wired all the way; why add the vagaries of wireless to all the other possibly problems you might have with those, even putting aside the security issues? Even when it's playing a TV station back I would imagine it's conventional cable, not pulling it in over the air.