yes indeed this is a strange situation.
The check on BSIC should perforrmed every 30 sec only !
The MS shall attempt to check the BSIC for each of the 6 strongest non-serving cell BCCH carriers at least every
30 seconds, to confirm that it is monitoring the same cell. If a change of BSIC is detected then the carrier shall be
treated as a new carrier and the BCCH data re-determined.