He'll be using Mavericks and I directed him to download drivers from inside Boot Camp Assistant. Voila, there is no 5.0, they are updated - Apple though is behind in updating support. Very behind. And also I see people using Windows 8 Dev Previews and other setups, I used Windows 7 64-bit on an "unsupported" MacPro1,1. Take with proverbial grains of salt, for where there is a will there is a way. Apple drivers and thermal management under Windows have always fallen short anyway.
Everything you want to know was in that forum thread though.
Boot Camp Assistant 5.0 would be Mountain Lion, not Mavericks and I don't have Mavericks. No mention yet of Boot Camp 6.
And I see you asked.
See this:
I tried to boot into Windows on my Thunderbolt drive in Apple Store's demo machine, it works fine