Probable Sprint model Motorola X Phone passes through the FCC
The AT&T variant was model number XT1058; the Verizon model showed up as XT1060; and, the Sprint model has shown up in the FCC filing as the XT1056. The device has LTE Band 25, which is only used by Sprint. Interestingly, it also has certification for HSPA+ 21 Mbps on the 850, 1900, and 2100MHz bands, but the documentation says that the device will be SIM-locked for all US carriers.
Additionally, the XT1056 has certification for NFC, Bluetooth 4.0 Low-Energy and Enhanced Data Rate, and 802.11ac just like we saw with the AT&T model.