The official Sony Xperia T Jelly Bean update might still be a few months away, but in order to give developers a sneak peek at what's ahead, Sony has released an early alpha ROM for the device. The Xperia T Jelly Bean alpha can be flashed using Sony's own flash tool, after unlocking the Xperia T via the official bootloader unlock utility.
A few caveats apply here -- radio functionality like Bluetooth, Wifi and mobile data is not included (likely for regulatory reasons), nor are Google apps. In addition, Sony says the UI has not yet been updated to reflect the final look and feel of the Xperia Jelly Bean firmware -- i.e. what's on the new Xperia Z. And crucially, if you unlock your Xperia T and apply this alpha ROM, you won't be able to update to the official Jelly Bean firmware once it's released. So this ROM really is one for advanced users and adventurous devs only.
Hopefully today's release will accelerate the progress of Jelly Bean-based custom ROMs for the Xperia T. If nothing else, we'd expect this to be hacked into something with working radios and Google Apps in a relatively short space of time. If you possess both a Sony Xperia T and a strong sense of adventure, you can find full instructions over at the source link.
Source: Sony Developer World Blog