Hi Harald,
I've created a new git repository (osmo-bts.git) for the BTS-side code. You can browse it at http://cgit.osmocom.org/cgit/osmo-bts/
So far it only contains an import of Andreas' osmocom-bb.git jolly/bts branch, and some minimal modifications like include path changes.
However, the code does not build yet.
Some code for BTS side already exist. I have made open source softBTS , This code build and if you run it, you can get 1st impressions for virtual BTS:
git clone git@github.com:softBTS/softBTS.git
Here is how to build and start software:
https://github.com/softBTS/softBTS#readme
Some members of this list already had chance to get code. Maybe can be valuable to someone else too.
fadil