Back to the OP's point. I read that they are checking all the engine numbers to identify the cars, so that will stop that part of the false claims. Insurance companies won't take your word for the value of the contents either, so you would need some kind of evidence that you left three laptops in the boot.
Law of averages says that they will find a good few stolen cars in the rubble - I guess those 'owners', even if innocent (I bought it from a guy in the pub) will not be getting any compo.