TEMS can measure the adjacent frequencies of the serving frequency. It will just measure the RXLEV, not taking care about which cell uses this frequency (as far as i know !).
When you lock on this frequency, you should be to camp on it and setup a call … if this is a BCCH frequency !
Are you sure it’s BCCH ?
If it is BCCH, then which cell is it ? maybe the cell is too far, or suffer very very bad interference in the area where you try to perform this drivetest.