After a few false starts, we believe we've found a list service that will meet the needs of this group. I've just added members of the EAST Resource Sharing Task Force to start, and if you could confirm this message works, and you can post to this list, I'll add the full list of resource sharing contacts. I've also added information about this list to the nascent wiki at:
https://resourcesharing.eastlibraries.org/discussion-list