[Update: A T-Mobile spokesman has informed us that the support page for the Google Nexus 4 is incorrect and that it is confirmed that T-Mobile will not enable Wi-Fi calling on the Google Nexus 4. ~ PhoneArena]
Here's a strange bit of news for the T-Mobile version of the Google Nexus 4 phone. Previous rumors and intel from T-Mobile suggested that their Nexus 4 device would not work with WiFi calling. Despite that, T-Mobile themselves posted a support document detailing precisely how to setup and use WiFi calling on the device. At this point it could go either way: a support doc printing mistake or the previous intel was wrong and the device will get the feature. Both of the leaked docs supposedly came directly from T-Mobile which is where the confusion comes in.
Just FYI, for those who don't know, WiFi calling basically allows your device to manually switch to your home WiFi network for voice calls when you are in areas of weak or spotty coverage.
Here's one big important side-note. The T-Mobile version of this phone is only $199 on a contract, but it is $499 off-contract. Either option does not seem to be a wise investment to us. The $200 dollar option locks you into a contract with T-Mo, whereas you can head over to the Google Play Store and get the same phone and use it without a contract on T-Mobile for only $299.99. So, for $100 more than the contract price you can have an unlocked device to use on whichever GSM carrier you choose. Conversely, for $200 dollars less than the unlocked version from T-Mobile you get the same unlocked device, which is obviously a no brainer. Why would anyone ever want to pay $200 more for the same thing and gain zero benefit?
Source: Nexus4Forum via T-Mobile