CGSociety talked to the Previsualization Supervisors for AJ Briones and Justin Denton from Halon Entertainment about the technology they used on Halo: Reach. Their focus was on the cameras, to make it feel like there's a cameraman actually holding them, and their solution was motion capture.
The OptiTrack Insight virtual camera system is a production-grade system, ready for the market. Tracked with optical motion capture, it provides an absolute coordinate system that marries user's virtual and real world together. Scaling and offsets can allow users to have a 'hand held' look, or zoom around a city, that is the benefit of a virtual world.