I would say since the RNS-E is a plug and play upgrade from the Symphony (with the correct adapter), the line out should work the same way. The adapter should definitely have the Bose config to get the line out wires, the Bose wire itself shouldn't hurt as all it does is to disable the internal amp in the RNS-E (AFAIK).
if/when i get the rns-e, i will report back. i know this is a total n00b question, but are there places to get fully ready-made kits? EU version ok, I just don't want to have to order from a million places.