Separate, OBMs training is shorter too I believe, as they have no safety critical duties, at least, they don't dispatch the train etc.
Commercial training, i.e. ticket selling etc. Is the same course, but they have specific trainers for each role, usually ex-conductors/OBMs.
I believe and this is just an observation, the have a batch of conductors training, and then once they're passed out a batch of obms will do their training. So usually a couple of courses a year for each role.