wiggy:
Not sure I'd call it a private cabin, if at home base we'd print out the paperwork in the company offices, brief ourselves and the cabin crew and then go through security with the aim of being at the aircraft about 45 minutes prior to departure. If we were down route we'd probably check bags on at a normal desk, clear security and then in all probability pick up paperwork at the gate or on the aircraft and brief on board. That's for long haul passenger ops..
All our on-line stations had a "ramp office" where we checked the weather and did our paper work. All of them were after we went through security.