The usage of multiple NCCs should be agreed between operators that provide service in the same location. From technical point of view it is possible to use multiple NCCs and it works fine. But don’t forget PLMN_PERMITTED otherwise you’ll face many problems and subscriber complaints!
When mobile station is in dedicated mode it performs periodical measurements of received signal level and quality of the serving cell as well as received signal level of adjacent cells. Hereafter mobile selects six best adjacent cells and reports them back to the network. The measurement report consists of BSIC,BA list index and received signal level of six adjacent cells. If mobile is not able to retrieve BSIC, the measurement result will be considered as invalid. Network element that processes measurement results (BSC or BTS, vendor dependent) checks the combination of BSIC and BA list index against adjacent cells database and converts it into CELL ID of the adjacent cell. If the convertion fails due to wrong BSIC it means that mobile has detected a signal from an undefined adjacent cell that uses the same frequency channel and the measurement result will be discarded.