The Nexus 7 with WiFi and Cellular has only been available with AT&T through the Google Play store on the past, and now a new version has appeared on Google Play which is compatible with T-Mobile.
The Nexus 7 for T-Mobile comes with WiFi and Cellular, and the device comes with 32GB of built in storage and a T-Mobile SIM card, it is available from Google Play for $299.
Google are showing delivery of 3 to 5 days on the T-Mobile Nexus 7 tablet on the Google Play store, and you can find out more information on the T-Mobile Nexus 7 over at Google Play.
Source Android Community