Troops and locals stop twenty car bombs from reaching the streets of Baghdad.

Yesterday a joint US-Iraqi force with help from local anti-al-Qaeda awakening fighters in the Adhamiyah district in northeastern Baghdad found and disarmed more than 20 vehicles rigged as VBIEDs in a parking lot.

This is a great find by any standards but the timing makes it all the more significant.
The significance comes not only from the quantity of bombs, cars and other resources that al-Qaeda has been denied the ability to use. It comes from the amount of frustration they have to deal with right now that all these preparations and resources are lost.

What makes me think that this will indeed frustrate them is that al-Qaeda chose to mass this great number of VBIEDs instead of deploying them to the streets one, or a few, at a time fresh from the factory. Two possibilities arise here; they either couldn't find the means and safe routes to deploy the bombs and so they had to wait for more favorable circumstances, which is good news since it means their ability to conduct missions has really been reduced to a great extent.
Or it could mean that they were planning for something big, and I'm more inclined to think that this was the case.

Apparently their cells in Adhamiyah (in my estimation the strongest remaining in the eastern side of Baghdad proper) were planning a spectacular comeback during which a wave of car bombings would have sought to undermine the improvement in security.
A week of several car bombings a day would have been seen as a huge setback following several weeks of great decline in violence.
Fortunately this has been prevented and whatever their plan was, it's vapor now and they will have to start all over again… That's if they don't get caught, killed or kicked out of the neighborhood, which seems to be happening quite often these days!