Hi Vanderley
BCCH/SYS-INFO 2bis is optional information sent on the BCCH – eg network to mobile station. The large number neighbour cells (freqeuncies) for DCS1800 and PCS1900 exceeds the capacity for the BCCH/SYS_INFO 2, and 2bis and 2ter are used to define and broadcast that information. See GSM0408
An MS which is primary GSM may ignore 2bis information.