If a vehicle requires a special license then there is likely a good reason. The person who is borrowing the vehicle may not have the same level of experience or expertise. Unless it is a specific rental business and the renter has show the proper tickets, specialty vehicles should be the responsibility of the owner.
If a person owns a specially-licensed vehicle, they bear some responsibility in who they lend it to. A person should not lend a car to someone if they know the person has five drunk driving convictions. A person should not lend a vehicle to someone that they know is not physically fit to drive it. They should know better.
If a person entrusts their specially-licensed vehicle to someone that they know or should know should not be operating it, then yes the owner should be held account to the actions of the person that they loaned the vehicle to. However, barring a showing that the owner knew or should have known that the person was a threat to others, then they should not be held accountable just because the person wrecked the vehicle in a garden variety accident.
This doesn't make any sense to me. I can understand if I loan a car to someone and a mechanical defect that I was aware of and neglected to fix caused injury or death to another, but if I loan my car to my very responsible and spotless driving record sister, and she accidentally slams into a schoolbus full of kittens and they all die, how in the world am I at all responsible?