From the Washington Post
"Since then, the cease-fire has been credited with helping to reduce
violence -- as have Sunni volunteer forces allied with the United
States and the addition of thousands of American troops."
""They can compete either through the ballot box or through militias,"
said a senior U.S. official, speaking on condition of anonymity. "The
Sadrists think they could make significant advances at the ballot box
as part of a backlash at the perceived failures of the government. . .
. They think they made a mistake in boycotting elections in 2005."
A little googling will get you much more I"m sure.
So, whats the point?
1) Sadr's cease fire was instrumental in reducing violence.
-But only one of several key factors.
2) Sadr was looking for a chance to increase his political cred (incidentally he was fairly successful at that).
The surge may have pushed him this way. If so the plan was probably to wait out the surge and then remove the cease fire.