We generally recommend VC units have auto answer turned off. However, after suitable, documented risk assessment, auto answer can be turned on so long as the microphones remain mute until manually made live. 
This is in the interests of confidentiality – it is possible that a VC unit’s screen may be turned off. If this screen also provides the audio for a VC call, people using the room may be completely unaware of an incoming call.
A recent internal audit of all the NHS Scotland systems found a small number of units which were set to auto answer with a live mic. Most have since been changed after discussion with the relevant health boards. We aim to complete all the systems in the next few days.