The very well-respected converters I talked to before getting my van converted definitely also worked on Calis, changing them to the owners' specification, so I would think it's possible to have work done.
There is a long thread on the T4 forum about book values and insurance, it depends on how clued up the insurer or loss adjuster is, as book values don't appear to work well for VW vans, either for sale or insurance due to vans being quite individual. Mind you, that's a very new van and should have lots of comparables...