I don't know if this is conclusive but I just noticed that if you turn the Surface Pro on BEFORE lowering the keyboard/cover that keyboard will respond when it normally doesn't. Yes, I do realize that it may be difficult to know if the computer was actually turned on since the display isn't visible and this may not be your normal process in using the computer. I lowered the keyboard almost immediately after pressing the power button. I only checked this twice, the reason I said it isn't conclusive.
I believe this is verified. I tried this 5 times so far and every time the keyboard was responsive.