I went to the Bultaco site and saw the "Rapitan" bike. The description says it uses ultracapacitors along with its battery. Other items of interest: a Hossack front suspension, and the claim of a huge increase in recovered energy due to their regenerative braking design. They claim, "the technology applied to the chassis maximizes the rear wheels’ adherence during braking, which enables a considerable electrical braking torque to be applied."
So this bike and the Sport version were to be launched in 2015. Any sign of it in the wild?