Yes, there are several ways to connect different AgendaX sites that do not share the same Active Directory Forest or domain, or are even in completely separate companies.
For example, AgendaX can scan the mailbox calendars on local Exchange servers and write the information to a local or remote database. A data source is configured between all locations (a specific port can be freely selected) so that all AgendaX installations know each other and write to a central database.
Details about the protocols in use can be found in the document Multiple Organizations Architecture and Protocols
