Still issue with getting the drawing override to work in python to display custom gl entities in viewport 2.0, so I turned to C++ based on the example in the 2012 api documentation since I finally got C++ code to compile for Maya.

Image shows pyMGL with a C++ node in maya 2012 viewport 2.0. The next stage is to bring better performance by mirgrating code from python to C++ and use things like vertex array and VBO while retaining the procesing-like syntax for scripted drawing. The current implementation is useful for small scale visual feedback from script but becomes very slow when number of entities increase to around 100,000 (without vertex array or vbo), so hopefully it gains better performance with the proper opengl.

reference on viewport 2.0:
http://www.scribd.com/doc/36964619/Viewport-2-0-API