If the Digital box is written into the Avants software then yes the Avant/Beo4 will be able to control the digital box. Many boxes are written into the software and the software can be upgraded by service tech for newer boxes. The best thing to do, pay a visit to your local store and they could recommend what box to use with the Avant.
I have two boxes controlled by the Beo4, one is free to air digital with DTV button and the other is digital pay tv on V.AUX. V AUX can be added to your list function for extra connections such as digital boxes, game consoles ect.