I don't know. Probably have to enquire. Such devices are implemented widely in a lot of indoor places like schools, colleges, auditoriums, etc.
I don't know how amplifying a publicly available spectrum band to a limited private space (home) is illegal. Sounds silly.
Say I boosted two or three of the spectrum bands that Airtel has been awarded through the auction process. If I am boosting the signal for personal reasons (meaning not reselling the spectrum by offering it commercially), in a private residential setup (our home), in order to access Airtel's own network, I don't see the legal issue of misappropriation of spectrum?
If I were to use that spectrum for another purpose, than that would be illegal.