Unless it is in or on their property.
I think you are referring to the property being in the care, custody and control of a business, such as a car in a body shop that has a fire. So I get what you are saying, but I don't think it would apply here. He has to furnish the tools, so even if they are in his work truck, he is probably responsible for insuring the tools. If he was required to leave his tools in their custody when he was not at work, then that provision could possibly apply.