The settings for this one

Your Photonic Glas-Ball is done !

Now we'll come to the most important Object in this Scene -
The PHOTON-COLECTOR
(the little PLANE between your light and the glass-ball)

Create a new MAYA Lambert-Shader-Node.
The settings are not important because we'll suppress all MAYA-Shaders for this Object
which means that mental ray takes only the MR-Custom-Shader-Nodes for calculation!

So ignore all Lambert-Settings and switch over to the
lambertSG Shading-Group !

Turn CASTS SHADOWS off - and the other stuff in the
Render-Stats Rollout of the shape !