The non-owner proxy has all the rights and responsibilities of a committee member but only if they were nominated for election at the AGM by an owner. My reading of Schedule 3 of the Act seems to suggest they have to be an owner to be a ‘casual’ proxy on a meeting by meeting basis.
3 Acting members of the executive committee
(1) A member of the executive committee may, with the consent of the executive committee, appoint an owner or company nominee of a corporation which is an owner to act in his or her place as a member at any meeting of the executive committee.
(2) The owner or company nominee so appointed is, while so acting as a member, taken to be a member.