The only possible logical explanation for how they changed the original BP plans, (Which were - New CAP, Near 100 % Collection, Wait on Relief Wells), is that they wanted to see how the well bore held up to increased pressure. That information could have been valuable to the operation of the Relief Well. But they were taking a big chance to get that info. So perhaps that means they are less confident about the Relief Well operation. At this point, a Top Kill is not a permanent solution. The Permanent solution is the Relief Well. They can try to flow mud and cement from the top again during the top kill, but that has already failed now twice.
THere is no pressure yet. They were supposed to start shutting vales to increase pressure, but the Obama administration stopped them.
Sure, it could be because they really want to be cautious. But remember BP has wanted to do this changeover for a while, the administration held them up, and then suddenly claimed they had “ordered” BP to do this new cap.
So I suspect that tomorrow we’ll have the administration issue a press release chiding BP for not moving more quickly, and insisting that they start the test.
They can’t have BP plug the well while Obama is on vacation, after all.