Maya Depth of Field Viewport 2.0

I was wondering if there was a way to access / modify the Viewport 2.0 Depth of Field effect. There is very little documentation about it. My first goal would be to make it more physically correct. ( Adjust blur amount to match an off-lline renderer ) Second make it work with transparent objects like in the attached image.

I have some OpenMaya 2 experience, though I assume this would be more a cpp override because of performance issues. This is what I found in the documentation. If any one has any tips / guides / articles how to approach this I would be really grateful.