1) Impossible scenario, if cell 1 and cell B are neighbors, they can’t have the same BCCH. It’s forbidden by the system. If it isn’t, then huge interference is bound to happen.
2) Cell B and cell C are neighbors of the cell A, and they both have the same BCCH. Just ensure B and C don’t have overlapping coverage, and they have different BSIC.
No problem at all.
If the coverage overlaps a bit, you’re going to see that HO from cell A to cell B might also be understood as a channel request (RACH) in cell C. And of course, a bit of interference on top of all that.