Pre-Collision -- does is work in stop-and-go traffic?

Does the pre-collision system work in lower speed, stop-and-go traffic?

Will the braking system kick in if it looks like your about to have a rear-end collision?

(I'm trying to figure out if the AT package is worth it.)

From Gearlog...

"Pre-collision system. An adjunct to ACC, the Prius pre-collision system warns you of an impending collision, pressurizes the brake lines for more effective stopping if you do come to your senses and slam on the brakes, snugs the seat belts, and if the driver doesn't take action, slows the car some, but won't stop the car completely. Some competitors' pre-collision electronics bring the car to a full stop. Not Prius. Toyota says it doesn't want to take too much control away from the driver."

I can tell you from personal experience that the seatbelt tensioning works at both high and low speeds. It makes quite the impression on the passengers!