When I got home from work this evening, issue 301 of Wargames Illustrated was waiting for me. The first thing I noticed was that the back cover was a Saga Battleboard for the Byzantines. Inside are the 4-page faction rules. A brief read-through of the abilities shows that the Byzantine units need to work very closely together. I'm guessing that these will be available as PDFs for downloads on the WI website in due course.
One thing that strikes me as being a little odd is that an empire which hired lots of mercenaries cannot include "Swords for hire" in their warbands.