Same way Getty know that your stills shots weren't taken by a camera on the approved list.
There's an article this month in
HD Magazine describing that the BBC are examining the use of DSLRs on a case-by-case basis..
Ian Potts who is an Executive Producer at the BBC and part of the approval process explained the BBC's approach to these new cameras: "Cameras like the 5D and the 7D are going through our R&D departments and our simulations but at the moment they are not cleared for use mainly because of their aliasing issues. Moire patterns are also a concern but these aren't new and cameras like the Arri D20 and D21 also show them. But the fact that the 5D produces a 22 megapixel image then brings that down to 2 for video without the necessary processing and filtering does concern us but the proof of the pudding is in the eating.
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Ian went on to say that at the moment the BBC is in the process of a massive tendering project to approve new HD cameras for use at the corporation and anything less than 50mb/s data rate is being looked at unfavourably. Results from the tender should be published next month.
Broadcast cameras will be using three sensors instead of one and the compression/processing taking place within the camera will be different.