If connecting a Blackmagic Cinema Camera via Thunderbolt to a laptop, can you record directly to the harddrive of the laptop? Which bitrate does have these recordings if using ProRes HQ422 at 1920x1080 @25p? And what's the real bitdepth of the image you get in this setup?
The Media Express software it ships with will let you capture video directly from the Thunderbolt port at 23.98p, 24p, 25p, 29.97p, 30p frame rates (from the tech specs page)
From the Wikipedia ProRes 422 page you will get 10-bit sample depth, and High-Quality comes in at 220 Mbit/s for HD resolution at 60i
Thunderbolt can handle 10Gb/s and SATA 3 can handle 6Gb/s so they will not be a bottleneck here.