I recently received this response from Apple:
"The application would need to allow remapping of a gesture or key command to the middle mouse button. If the application does not support this then you would need to connect a mouse with a middle button.
For additional support for the MacBook Pro, OS X and key commands, we ask that you please contact AppleCare via the web, telephone or use the Express Lane link to begin an online support session."
Therefore, this functionality is dependant on third party applications ability to allow users to emulate a middle mouse button using keyboard comands (as Blender does). I am pretty surprised that there is no native (mouseless) MMB input options for MBP.