You cannot subscribe one Northwestern listserv to another Northwestern listserv, as it will produce an error. However, it is possible to set one listserv as the sub-list of another listserv with the same result.
Sub-lists can be configured only by the LISTSERV system administrators. The change must be approved by an owner of each listserv which is to be modified. If the listservs share an owner then it is best for the request to come from that owner.
Have the owner(s) send an email to servicedesk@northwestern.edu. They must identify which listserv is to be the primary listserv, and which ones are to be sub-lists; for example, if you want to "subscribe" listserv A to listserv B, listserv B would be the primary, and listserv A would be the sub-list.