Sony's Xperia Z Ultra has first appeared at the FCC on June 25 - the same day the handset was officially announced. However, that version did not have LTE. Now, a new FCC filling is showing an Xperia Z Ultra with LTE - bands 2, 4, 5 and 7. Since it also has 1,700MHz HSPA connectivity, this version could be released by T-Mobile USA (which uses LTE band 4).
T-Mobile is already selling the slightly older (and smaller) Xperia Z, so it's not that hard to believe that it wants to add more Sony handsets to its portfolio.
Unwired View , LTE-ready Sony Xperia Z Ultra hits the FCC, it's T-Mobile friendly, LTE-ready Sony Xperia Z Ultra hits the FCC, it's T-Mobile friendly