It looks like Bill drove that dark-blue Model S that you could see around 0:50. You can tell that it's not a Model X from the interior seat configuration.
Bill is a known 959 enthusiast [1]. Considering that only 345 were ever made and only a handful of those were imported into the US, I'd say that car is very likely his.
[1] https://en.wikipedia.org/wiki/Porsche_959#.22Gates_959.22