Interesting discussion.
Is it possible to fork an incoming call to be picked up by OBi IVR (AA), while continue to ring the actual phone? This way, assuming intercom panel send in-line DTMFs once the call if picked up, it could be setup for an automated door opening upon entering a password in IVR, while still preserving the legacy, human call handling, where upon phone being answered, IVR would cease processing and let human press the ford rbtry button.
I'm not familiar with OBi AA functions aside from glancing over them in a manual. The built in IVR didn't seem to be very robust, by perhaps someone smarter then me can chime in here.