Insurance companies are only liable for the costs that their policies obligate them to pay. If the insurance policy included towing coverage, then the insurer would have to pay--at least up to the policy limits. If there was no towing coverage, the insurer does  not have to pay--remember: insurance policies are contracts, and only oblgiate both parties to the terms of the contract. If the insurer does not have to pay, it would be the car's owner who is responsible for the cost, though he may have grounds to sue someone else--e.g. an at-fault driver, if some other driver caused the accident--in order to seek reimbursement of his towing expenses (and of other costs or damages, too).