Carrier update files are small, and do not involve the ROM. What this means is that the version of iOS on these devices will remain the same: 6.1.3. This carrier update will, however, allow devices such as the AT&T iPhone 5 to run on any LTE networks that T-Mobile might have active across the U.S.
T-Mobile's LTE network is live in seven cities: Baltimore, Houston, Kansas City, Las Vegas, San Jose, and Washington, D.C.
Here's what the leaked document says:
The T-Mobile Carrier Update is a minor iOS software update that enables official iPhone support by T-Mobile. When installed, the software update enables a handful of capabilities like Visual Voicemail, MMS Settings and Network/Device optimizations that customers do not have access to today. On April 5, the software update will begin being pushed via OTA to all iPhone devices on the T-Mobile network with iOS 6.1.x or higher.Those running jailbroken iPhone 5s, rather than AT&T unlocked or factory unlocked iPhone 5s can resort to the following method, if they don't want to wait for April 5:
- Open Cydia
- Tap “Manage” and then tap “Sources”
- Tap “Edit” then tap “Add” and put the following URL into the text box: http://v.backspace.jp/repo
- Once the URL is entered in tap “Add Source” and allow for it to download all of the repo’s info and packages.
- After your iPhone has refreshed, tap the v.backspace.jp/repo field or go to the search bar and find the package CommCenter* patch…
- Once you have found it, install it and then reboot your iPhone once completed.
- After the iPhone has restarted, open Cydia once again.
- Search for iFile. The free version includes basic features. You will want to purchase it to take advantage of all of the features.
- Once you have found it, install it. No reboot is required, though you can do it just to be on the safe side.
- Once iFile has been installed, close Cydia and click on this file from your iPhone and click “Open in iFile”
- Once you’re in iFile tap “Unarchiver” and 3 files will show up above T-Mobile LTE.zip
- At the top, tap “edit”and tap the dots with a check mark next to carrier.plist, overrides_N41_N42.plist, and overrides_N41_N42.pri
- Tap the clipboard icon at the bottom and tap “cut”
- Now tap “done” at the top and tap the house icon at the bottom then tap Library, then tap Carrier Bundle.bundle (the one in blue), and then tap edit at the top again and tap the clipboard icon. Tap “paste” and it will auto inject the carrier files into the carrier folder overwriting the other files.
- After the files have been placed, exit iFile and restart iPhone. After the iPhone restarts, allow it to acquire signal and display the T-Mobile logo then go to where you edit the APN settings (Settings – General– Cellular) Once that is done, enable the LTE toggle.
T-Mobile will begin selling its official iPhone 5 on April 12.