According to GSM 02.82:
Served MS:
+ If BIC-Roam is active, registration and/or activation of CFU is permitted, and BIC-Roam becomes quiescent.
+ If CFU is active, activation of BIC-Roam is NOT permitted. The MS shall be informed of this supplementary service incompatibility.
Forwarded-to MS:
Calls forwarded to a subscriber having BIC-Roam active and operative, will be denied as any other incoming call to that subscriber.