Microsoft's Greg Sullivan confirmed the codename for the company's recent push to low-end Windows Phone devices at Mobile World Congress today. Describing Tango as "an engineering project," Sullivan explained that Tango isn't an update per se but rather a collection of elements that make up a broader effort to reduce the cost of Windows Phones. This engineering work included a focus on ensuring that devices could make use of the majority of existing Windows Phone features using just 256MB of RAM.

All of the software features that ship on Windows Phone Tango devices will be made available to existing handsets, including some improvements to MMS and an SMS bug fix. Microsoft isn't saying exactly when that update will be available, but the company has not yet started testing it with carriers. Sullivan explained that once Microsoft has finalized a software build for its 256MB of RAM Windows Phone devices, it will then seed it to carriers to test on existing hardware. Microsoft says it expects the first low-spec Windows Phones will launch in Q2 2012, so the update could arrive in April at the earliest.

Sullivan also touched on Nokia's Chinese plans in an interview with us earlier today, explaining that the company "worked closely with Nokia in targeting the new lower costs devices." Nokia "helped elevate the priority" of bringing Windows Phone devices to China says Sullivan, and devices are now expected to launch in the coming months. Despite the close work between the pair, Sullivan says it will benefit all of Microsoft's Windows Phone partners having Nokia add components directly into the Windows Phone codebase in future. Microsoft isn't discussing exactly how Nokia will contribute software features to Windows Phone, but the Finnish company revealed to us this week that maps and location is a big part of that effort.