I think Pan is right about Same BCCH but different BSIC case. A cell is identified by the BCCH-BSIC combination not the BCCH only. MS is idle mode needs to decode the BSIC of neighbor cell at least once in 30 seconds to ensure that it is monitoring the same cell. If BSIC is different then it will be regarded as a new cell and then MS will decode the BCCH SIs to find out that this cell belongs to vPLMN so no reselection to the cell till every hPLMN cell becomes unavailable.