You have to feel for Sony Xperia Z owners on T-Mobile in the US. Whereas Xperia Z owners elsewhere got hold of the Android 4.2.2 update back in June, it is only now that the update has been released on T-Mobile. New build version 10.3.1.E.0.191 will upgrade you to Android 4.2.2, including camera access from Lock screen and software stability improvements and “improves handset rebooting when dialing a call”. The update can be downloaded over the air or via a computer.
Thanks @inthelab88!