Dear BOAC,
Thanks for the input.
Checked the link. Also checked FCOM. The term used now is Engine Vibration, though I do recall hearing the term AVM too somewhere. No mention of any inhibit conditions, unlike other inhibits which are mentioned in every chapter. (Found it useful to search for specific words in the FCOM using Adobe, so you can examine every single occurence.)
Re autopilot engagement, there are no cutouts on ground, otherwise you would not have to disengage AP after landing off a dual autopilot approach. You can (probably) check Autopilot operation during taxy by going Heading Select and watch the controls try to put on bank as you turn off the heading. Haven't done this myself, but will check it out. Should work as it would on every other aircraft fitted with a similar autopilot function.?