What is the "innovative" arrangement with the FISA Court about the NSA program?

After a year of argument about the Adminstration's warrantless approach, there is now a new arrangement. But what is it exactly? Orin Kerr speculates:

[I]t sounds to me like the FISA Court judges have agreed to issue anticipatory warrants. The traditional warrant process requires the government to write up the facts in an application and let the judge decide whether those facts amount to probable cause. If you were looking for a way to speed up that process — and both sides were in a mood to be "innovative" — one fairly straightfoward alternative would be to use anticipatory warrants....

What's the mystery legal development that helped make this possible? If my guesses are on the right track, it's probably the Supreme Court's decision in United States v. Grubbs, which was handed down on March 21, 2006. The Grubbs case is the first Supreme Court decision approving the use of anticipatory warrants.