No he can't really make that decision himself, and actually this is outside of scope of what you should be doing. You need to bill accordingly with proper diagnosis and accident information, the situation with his deductible is between him and his carrier. You should probably contact the PIP carrier and see if they have an open case, obtain proper verification and info needed and bill them. If claims get sent to health insurance carrier first they are going to deny for accident or third party recovery anyway as the PIP would be primary. Some indeed can use their health insurance carrier as secondary.