PassThrough Plus Activation with Keyboard?

I'm interested in the Rift-S and am looking forward to the Passthrough camera. I am an avid VR flight simmer and was wondering if the ability to toggle the camera would be only hand controller based or if there would also be keyboard assignments to toggle it as well. I use VoiceAttack to issue most of my VR commands that are then assigned to keyboards presses and was hoping to be able to toggle the Passthroughj camera this way as well. 

Does anyone have any knowledge on how it's deployed other than with the hand controller?
I hope an assignable key press is an option since I do not use the hand controllers when flight simming in P3D or DCS.

Thanks in advance 
Joe