Maya 2012 uses a customized version of Nokia's Open Source Qt 4.7.1 framework.

If you want to use Qt in your Maya plug-ins then you will have to use the same modified version as Maya. That will require that you build a local copy of Qt from the customized source.

A copy of the customized Qt 4.7.1 source is available from Autodesk's Open Source web-site (http://www.autodesk.com/lgplsource) and includes text files describing how to configure, build and install Qt for each platform supported by Maya.