We have experience in building asterisk ,openbts ,yatebts ,openbsc,osmocom.
We are also gave a presentation on gsm security weakness in India. we will complete this project in 10 days. hardware should be provided by employer. we already have ettus n210 ,bladerf ,RAD1 devices with us.
Limitations of OpenBTS
1) one can listen to only outgoing calls
2) as usrp n210 dont have power amplifier coverage area of imsi catcher is very low.
3) to increase coverage area you will need power amplifier and LNA ,duplexer
we can help you to buy devices from market which can give you good coverage.