As you can see in this picture referenced by this blog post, somebody is having real fun using the BS-11 and OpenBSC for GSM wardriving.
Please note that the BS-11 is a 200W AC powered device, so you need the entire trunk full of lead batteries and a reasonably sized UPS to provide it with power.
There are much lighter setups using a laptop and a nanoBTS, but then those setups are likely a factor 10 more expensive (and provide less RF power).
But what this all tells us: GSM wardriving has started. More security researchers are looking into GSM security than a year ago, much due to the successful growth of a community around OpenBSC. Many people are only starting with GSM and mainly using/playing with the software, the number of actual contributers to the code is still small...
On a larger scale, you can see that GSM insecurity is finally going to become a much more popular topic, with more people able to demo the various long-known issues such as lack of mutual authentication and insufficient threat models/analysis during protocol design.