There must be at least 30 companies in Europe, including Trek that is on the EU bandwagon also, that spec the Bion x for their e bikes. It is super easy for them to just bolt a kit on one of their existing frames, but as the one guy said they are expensive and there are certainly less expensive and more powerful hub motor kits available.
I find it interesting though that almost all the companies that are starting with a blank slate are going with a form of bb drive system. Bosch is working with Cannondale on and the Panasonic and Yamaha drives have been in use for the last 10 years.