The ARPAnet coordinator could, at any time, do a review of the BITNET
list.  All of the servers would send him copies of the current list.
He would then know exactly who was on the BITNET side of the list.
 
As far as adding users, since the ARPAnet coordinator would be the
list owner, he could add users to the list himself, when he received
requests.  In fact, he would only have to add the user to any of the
servers, and LISTSERV would take care of adding the user to the correct
server...
 
Hal