I know I've had a CD in my car with the vocals only tracks excerted from the SWW Dual Disc, but that was about 8 years ago. This video definitely sounds more "robotic" to me than I remember it and it may be that it stems from the Rockstar video game where it sounded a bit different.
It sounded layered to me back then, like Jon had sung the high part once and after that it was just copy and paste.
Since I'm not that much of a technician I can't say whether it would've been possible back then or not, but autotune as we know it nowadays was invented in the mid/late 90's.