I may have some ideas. The best option would be to develop a Control4 driver to interface directly with the ISY.  I've always been interested in developing Control4 drivers.  I don't install Control4 currently but I've been interested in it. Alternatively there is a Control4 driver for integrating external systems via TCP and HTTP commands.  There's another driver that can be used for sending HTTP and TCP commands.  Perhaps there's a driver that combines both.  I believe drivercentral