I would be doing a three way telecon with the VW manager, insurance co claims rep and yourself. Talk beforehand with a claims rep so he can be the bad guy. Give the VW shop a deadline and get a commitment to pull the car from the shop if the deadline is not met.
I think that should get some attention. Alternatively, pull the car today out of the shop and check with the insurance co about paying for the tow bill. The insurance co should be on your side for the timeliness issue, for customer satisfaction reasons.