Hi
In my experiece with IHC & BCM, Bank communciation management approval was done only when F111 is executed to send the file to external banks.
Due to the fact that you need to use the program RFFOEDI1 - IDOC message from F110 in subsidiary to IHC, I reckon that you cannot route F110 to BCM in subsidiary, as Payment medium workbench needs to be used in BCM, therefore we used the approval process for subsidiary F110 - proposals and payment runs.
So the process flow should be Process flow: F110 in sub -> IHC in Head office -> F111 in Head office -> BCM in Head office -> out the door to external bank.
hope that this helps
cheers