This would be an odd situation seeing that Twitter integration is a feature of Windows Phone and not one of HTC. Just to be sure, we reached out to Jay Bennett, who is on site at the London unveiling, and he sent us this snapshot of the Titan's account set up screen.
While slightly out of focus, we can clearly see the option to set up your Twitter Account on the HTC Titan. That would be Jay's finger in the photo. I guess we can now say he's got a famous finger.