If yes, can it [silent call] be done in OpenBSC or any such way exists to do this or any other alternative does exists?

Please check out http://ftp.osmocom.org/docs/latest/, you can find OsmoNiTB / OsmoMSC user manuals there. Silent call feature is supported, but not documented. Feel free to contribute!

With best regards, Vadim Yanitskiy.