So far as Watson goes, "he" does receive a text file which is sent at the same time the answer appears on the screen. And I'm pretty sure he is signaled in some way when Alex is finished reading the question in order to make sure he doesn't press the button before Alex is done (I think your button gets locked out if you press too soon).
I think Watson's big advantage is that it takes a human a second or so just to process and comprehend the answer on the screen. In that time, Watson can do billions of calculations. It's not that the questions are so hard for humans, as CG's link says, they know the answers 70-90+ percent of the time.
So to even things up, they should try delaying when Watson gets the text file. I'll bet if they delay it just one second, it would even up the game a lot more.
