Hi,
Its not required do the init BX again.
BX we need to do init only once.
About init of BF or UM:
if your existing inits have any selectiones based on company code then you may need to do the init.
if you done init without any selections then you don't need to do the init again.
Maintain company code master data and run Attribute change run.
later you can run transaction data load. will have new company code as well.
Thanks