indeed, when a MS goes to the cell n2 by doing a Incoming HO, a HO ACCESS is sent to TCH(n2) with BSIC(n2)
will be understood as a CHANNEL REQUEST on BCCH(n1) with BSIC(n1) = BSIC(n2)
This will happen because the TCH(n2), on the TS4 -let’s say-, is scheduled at the same time as the TS0 of TRX1 of the cell n2. The 2 cells are not synchronized. When MS sends HO ACCESS to TS4 of n2, it will also be heard in cell n1, in the TS0.