They cut off the top of the riser. There is no way to bolt a BOP Stack onto that. There has been a failure inside the BOP Stack. The Engineers know this and this is why they will not run drill pipe inside the 9-5/8 inch casing which in all probability they could not anyway. The failure in all probability is at the casing hanger for the 9-5/8 inch casing. The oil and gas is coming from the formation around the outside of the 9-5/8 inch casing. You could fill the casing up with cement and the well would still flow!
That well will flow until the relief wells are drilled into the production zone and they kill the well and fill it with cement. Hopefully BPs effort to attach the new riser assembly will collect the oil until they have killed the well.
What are the chances of THAT? My dad sold for Cameron for years (long ago) and in all my years of selling drilling equipment I've never heard of them all failing.