Confirmed: US Tmobile.com Sensation 4G works in Europe.
This question seemed to come up a few times in the past, not sure if it was properly answered.
Got a Sensation 4G from TMobile Store in NYC last week. Brought it to the UK, and it is able to connect to the 3G network here no problem.
It did not even need un locking to connect to TMobile UK Network.
Funnily Enough, it never says 3G / H, it always says 4G on notification bar.