I can only speak from our personal experience. I attended training with my daughter and Mo, I am the secondary handler, for reasons just like what you mention. When she has been in the seizure unit, or has had surgery, Mo stays at the hospital with her. Mo has also gone with her by ambulance when she had been out and gotten injured. Mo wears a vest, clearly marked SERVICE DOG DO NOT PET. He has a pouch that is marked MEDICAL INFO and contains her medical history, meds, drs and emergency contact numbers. He has been allowed everywhere except into the actual OR. A secondary handler is required for times she cant care for his needs, like to toilet him when she is in surgery, etc. He has only gone by ambulance once and they paramedic called me. When I got to the ER my daughter was in a room with MO, and he was laying on the floor watching her and the medical team.