It doesn’t make sense that all call drops are related only to the interference in the BCCH.
When calls are in non BCCH TRX(u can either use single TCH or Hopping for that TRX),then drops due to interference on that is because that/those TCH frequency/frequencies are getting interferences.
And calls when are in BCCH,interference due to co or adjacent BCCH.
It depends calls are where….in the BCCH TRX or in the non-BCCH TRX.
But BCCH should be more priority..as according to u..SD are on BCCH..so it should be keep clean…to reduce other drop like SD drop…in your network.