I have written two addons that allow XBMC to interface with an ISY-99 series controller. They are both in the standard XBMC repository. One is called ISY Browse. With this, the user can browse through and activate the nodes and programs on the ISY controller. The other is called ISY Events. With this, the user can set nodes and programs to be automatically activated when an XBMC event occurs.
ISY Browse is listed under programs.
ISY Events is listed under services.
Instructions and more details can be found here: https://code.google.com/p/isy-events/