Well, maybe. In my view, the credit card's insurer, before paying a loss-of-use claim, should be entitled to view the same evidence of loss that the car rental company would have to produce in court if the rental company sued the renter for loss-of-use damages. In court, I doubt that the rental car company could hide behind the "proprietary information" argument to avoid producing documents the court deemed relevant to determine if the claim had merit. The problem here, I think, is that most loss-of-use charges are so relatively small that the rental car company would normally just turn the matter over to a collection agency, and get whatever they can on the claim, rather than sue. And many renters would be too worried about possible adverse effects on their credit reports to refuse to pay the loss-of-use claim, or at least a negotiated settlement of a loss-of-use claim.

By the way, maybe I'm missing something, but how would turning utilization and related records over to an insurance company amount to sharing proprietary information with other car rental companies? Would insurers normally share such information with other car rental companies?