Hello Pix,
Lately I had been trying to find out more info about this issue.
In 3GPP TS 05.08 version 8.23.0, particulalry in section 7 it has been said that if 8PSK is used in BCCH carrier then cell selection, reselection and HO procedures invloving these cells will be somewhat sub-optimal.
If you have time could u plz check it out.