Could you quote the part of the text which indicates that the Orthodox churches wrote a specific response to BEM? I haven't heard of such an official response from any Orthodox church. In the document you referenced, this is the only statement I could find that seemed relevant:
19. Future discussions can build upon work already done together over many years, including The Toronto Statement; The New Delhi Statement together with the Orthodox response; The Canberra Statement; The Common Understanding and Vision of the WCC; Baptism, Eucharist and Ministry and the church responses. It is important to take account of work already done on ecclesiology. The leadership of the WCC is asked to promote that work both within the structures of the WCC and by encouraging churches to continue in a process of reflection and response to that work.
It states that there was specifically an “Orthodox response” to the New Delhi Statement, but then it just says “Baptism, Eucharist and Ministry
and the church responses.” To me it is not clear whether this refers to an Orthodox response that was actually made, responses from non-Orthodox “churches” which would be discussed with the Orthodox as part of the Special Commission process, or hoped-for future Orthodox responses to BEM. Is this the text you are referring to, or does it say somewhere else more explicitly that there were one or more official Orthodox responses?