The [http://tier.cs.berkeley.edu TIER] research group at UCB is actively working on the OpenBTS project. The goal is to allow for easier programming of applications running concurrently with OpenBTS. This is done by modifying [http://freeswitch.org FreeSwitch] to better integrate with OpenBTS. 

We also have a running 10W BTS in the city of Berkeley covering campus and nearby areas. Contact us if you're interested in being a user of the system. 

The lead developer is [http://www.cs.berkeley.edu/~kheimerl Kurtis Heimerl].