MHoy:
I don't fit your categories of insureds, but I have a comment anyway.
I have a friend who formerly owned a van leased to a major carrier. He hired a team, that I introduced to him, to drive that van. Both parties were happy and financially rewarded by the relationship, Until the team was involved in an accident that caused considerable damage to the van.
The accident was ruled preventable by the carrier and, admitedly, the drivers were indeed responsible for the cause of the accident. The performance agreement between the van owner and the team did not address the insurance deductable issue. In the end, the team refused to pay the deductable and the owner was stuck with the damage caused by a non-employee party.
I think the owner should cover the deductable for a non-preventable accident and the driver, if not an employee, should cover the deductable for a preventable accident. In either event, the insurance premiums should rest with the owner.