R2's wakeup was too convenient for words. I mean, if if BB8's data was the key the R2 waking, I coulda bought it. But not as-is. Cause and effect beats coincidence in drama.
I think there was more to it than that. R2 didn't wake up until Rey arrived. R2 has always been the droid that knows everything that is going on. It would stand to reason that Luke would have given R2 instructions about who should find him. Rey comes calling with her, for lack of a better word, awakened Force powers, and Anakin's lightsaber. R2 knows who should find Master Luke, and turns on when he is needed.