Short Answer: No.
Longer Answer: The XBMC and MythTV crowd have done some work to get CableCard tuners to work in Linux. While some of this work might be translatable to *BSD, the fact of the matter remains that the movie, television, and cable industries do not actually want CableCard to work. CableLabs have been deliberately dragging their feet implementing the FCC's mandate for open access for at least the last seven years that I've been paying attention. Time-Warner and Comcast would much rather you take one of their custom-kluged set-top DVRs for a mere $19.95/month each. They only support CableCard on sufferance and, through conscious neglect, make the CableCard experience as unpleasant and unreliable as possible.
Assuming you can get a CableCard tuner to authenticate to your local cable provider (difficult, but not unheard of), you still won't be able to decode premium channels because your setup hasn't been blessed by the Cable Cabal as "compliant," which is code for, "Refuses to let you, o plebian subscriber, do anything with recorded content except watch it, in a single location, in only the manner we prescribe" (an Open Source CableCard application would naturally (and correctly) put the user in charge and ignore such childish demands). So you'll only be able to decode and record non-premium (ClearQAM) channels.
The only systems that I'm aware of that work well with CableCard are TiVo and Windows Media Center.
Do a Google search for "cablecard mythtv xbmc" to get an idea of what you're up against.
