It seems that there are only few of them existing. Most probably only three, although there are far more back-to-back recumbent bikes on the roads. It is a bit strange as people are more interested in recumbent tandem trikes than bikes because they are afraid of manouverability and problems with balance. The main two reasons why there are only there or so B2B trikes are that it is pretty complicated to design a trike like this and to build it and the second would be the lenght of the vehicle as it is even longer than the B2B bike.
The picture shows an ICE version and you can read a bit more about it here. There is also a little video showing it in work.