Hybrid technology based on a diesel engine is available - the Peugeot/Citroen gruop recently launched this. It's available in cars such as the Citroen DS5 or Peugeot 3008. (Though the roads tests I've seen suggest the automated gearbox is dreadfully jerky - no doubt that can be improved).

I don't think it's a "no brainer" for vans. A few thoughts.
(1) The diesel hybrid power-train is more expensive than a plain diesel engine. Most commercial vehicles are bought down to cost - the buyers won't stand the additional purchase cost.
(2) Fleet managers are oonservative and slow to adapt to new technology. Their vehicles do huge mileages - but as this diesel hybrid powertrain is so new, there is no "real world" reliability data
(3) The battery pack adds weight - which reduces the available payload of the van. My hunch is that this will be the most difficult hurdle to overcome.