The Comcast Xfinity X1 uses the XMP IR protocol, which is notoriously difficult to learn.  It does not employ control commands followed by feature commands, but I doubt there is anything you can do to the ML remote to make it learn the XMP protocol.

Of course any Harmony line of remotes can handle all of your components.  A Sony RM-VLZ620 is much cheaper, and it can shoot the Sony and Xfinity signals out of the box, and can learn the ML signals.