It would definately be SSI, but weather or not Borg and them actually implemented that style of integration, I do not know.
In order for you to be able to do that, they would have to run the "who's online" FROM ultimatebb.cgi.
Just like this message. This post is pulled by ultimatebb.cgi (notice the '?' after ultimatebb.cgi). Everything after the '?' determines what shows up. So, if Borg and them want to, they can make "who's online" able to be called after the '?'. Then, and only then, can you use SSI to pull it up.
Get my drift?
The only other way to do it would be to make it an entire sepereate CGI file for "who's online" and then require it inside of ultimatebb.cgi, which I doubt they did.
For the record, I would like to be able to do this too, so I hope they do make it able to be called by SSI!!
