John, I don't know if this is still a live issue for you but I thought of you while reading up on the Fiery Controller Option for the C2800/C3300 and the C4000/C5000.
In an FAQ Document under wireless printing options it states, "When printing from USB removeable media, the Fiery will print Postscript and PDF File formats. If the Fiery has internet access and the Native Document Conversion option (i.e. EFI PrintMe) then you can also print native Microsoft Office Documents from your USB..."