Originally we had looked at using larger digital cameras but when I looked at the script I realised that the only way for this to work (film people for real without them realising) was to make the cameeras obvious. Camera hides would be noticed but a bunch of news crew would be so commonplace that they could be right in front of people and they wouldn't notice.
Becasue of this I suggested the F900 and Simon was shocked "but you hate those!" well yes, but mostly because they were misused and anyway Sony had just launched the /R version and it finally worked!!
So, we had 6 of these, 5 right in front of people with an operator and AC and the sixth on top of a building with a 55X stabilised zoom lens.
Everything was wireless linked back to a central area with pictures, timecode and audio. A recipe for disaster but it worked.
The only problem we had was when the client saw my monitors and panicked, I'd loaded a log file into the cameras so my monitors were looking very flat and de-saturated, I'd made sure that the client monitors had compensaton applied to make it look "right".
We had to go to telecine the next morning to prove that my "flat" pictures worked.