Halliday & Matthiessen (2014: 343):
In the identifying type, it is normally possible to add a feature of agency (an Assigner) provided the clause is operative (Token as Subject): thus, to (‘which is Tom?’—) Tom is (serves as) the leader corresponds an agentive such as they elected Tom the leader; and, with second order Agent, they got Tom elected the leader. We have seen that, with such decoding clauses (those where Token = Identified) the receptive is in any case rather rare.