This passage from Joel Achenbach's A Hole at the Bottom of the Sea: The Race to Kill the BP Oil Gusher was pointed out to me this morning. The relevant paragraph is at the top of this page which I will try to embed below.
In other words, there was at this moment an opportunity to draw a pretty decent bead on the rate of flow from the well. (The accuracy of such a calculation should be within plus or minus 10%.. or so I'm told.) BP is disputing the numbers using a flow rate formula based on an estimate of the amount of oil that was in place in the formation to begin with. Which, if I understand this correctly, is far more open to interpretation. In any case, Achenbach is suggesting that the calculations made after the Q4000 was shut down are not too different from actually having a "meter" on the well at that point despite Judge Barbier's statement to the contrary.