I've read that Patriarch Athenagoras did consult with the heads of the Holy Orthodox Churches about rescinding the "anathema," but I've read much more information that he did not, that he acted unilaterally, though I imagine the Holy and Sacred Synod of the Ecumenical Patriarchate approved the action.
It's a fair question because Patriarch Michael convened an Extraordinary Synod of the Ancient Patriarchates at the time which acted to anathematize the Church of Rome, and was recognized by the Holy Orthodox Churches thereafter, so doesn't it become the property of the Holy Churches, and not just the Church of Constantinople?
I don't think the anathema Cardinal Humbard placed upon the Holy Table of the Cathedral of the Holy Wisdom, the seat of the Patriarch of Constantinople, that anathematized the "Patriarch Michael and all who follow him," should be viewed as a "void anathema" or that it had "no weight" because neither of the Church's took issue with its competency at the time or any time thereafter, in fact, it was recognized as an anathema, although it was generally believed that it would be a temporary situation, until 1204, of course.