I haven't been able to find a newer one as descriptive as that one. Some webpages describing the IRCX commands exist on Microsoft's labyrinth of a website; but most of them (if not all) don't go into detail about the error messages, channel properties, etc.
It's even funnier that by "Sep 9 2000" (when the Microsoft Exchange Chat Service Server 5.5.2653 was created) not all of the IRCX functions had been implemented on Microsoft's own IRCX server.
Although that document is obsolete, I can assure you that the ACCESS and PROP commands still stand as described in that document on Microsoft's IRCX server version 6.0.6249.0 (created on "Jun 18 2002"). Also, I haven't found any differences from what is described in that document for other commands and how they currently work, but I cannot guarantee that there aren't any.