srw
It's a bit more complicated than that...
Fairly cheap really - low millions at most. Compare that with Selby (reportedly £35m or so) - and there's apparently been one in Germany recently for about the same.The insurance claim form will look interesting, especially the diagram of the accident!
My prediction is that the department of transport will insist that at great expense every single bridge in the country is inspected and a large number of them upgraded - at the expense of rail passengers. Compare that with what would have happened if no train had been involved and it had just been a road incident: absolutely nothing. We have a very skewed appetite for risk in this country when it comes to transport.