Mostly Tacx, whilst warming-up for a TT they use the Satori's(very good and not too expensive, I use them myself very happy about those). I guess they use Tacx Bushido at home because they can than read their poweroutput and heartrate etc...
I'll chime in that the Computrainer is a popular winter indoor trainer for the pros. Generally it is regarded as being more heavy-duty than the Tacx or Elite trainers.
The Tacx Bushido is nice because it does not require a power outlet.
I think which ever one sponsors them. But I would think if they have power on the bikes they wouldn't bother with a power meter on the trainer. Also they tend to go to spain or some place to train when the weather is really crap.