Been a while since I listened to either of these tracks, but nearly fell of my chair when I just realised that one samples the other. You can actually hear Prince's voice on Like A Prayer [Dub Beats]. The exact sample is "That skinny motherfucker with the high voice".
Madonna - Like A Prayer [Dub Beats]
Bob George - Prince
So, still think Prince isn't the one playing guitar at the start of Supernatural?