[TimG]

The carriers insurance should be the first/primary one to pay the claim. They will probably pay out of pocket for $2,500 in damages as I'm sure their deductible is higher than $2,500. They may just want to keep it from going their claims record if the damages are lower or near their deductible. My guess is they will work with you directlyto get it fixed without the involvement of their insurance carrier.
If they are not handling your loss in a satisfactory manner or if they just won't pay, turn it in to your carrier and have them handle this loss under your policy. They will subrogate against the negligent party, the motor carrier. They were negligent because their straps failed or weren't mounted correctly. Your carrier will squeeze them for the funds. Insurance companies like to subrogate or collect from the negligent party after they pay a claim that wasn't their insureds fault.