I got past the AGT running straight from inside the tunnels to the back of the Barracks with a stealth trooper. I had full health and armor and when I made it to the back of the Barracks I had something like 23 HP left. Unfortunately someone coming around the power plant saw me and uncloaked with 23 HP I didn't stand much of a chance. It can be done. I think what is causing most people to fail is that they get in a fight or set off a mine on the way to the back tunnel, and then they try to make the run without full armor or health. That's death.
Also, many people have the dumb habit of standing in the doorway of the tunnel for a few seconds, which lets the AGT shoot them. You should run down the tunnel and out the exit towards the Barracks without EVER stopping. If you pause by the doorway and the AGT gets any free shots on you, well you're not going to survive the run at that point.
[ February 21, 2002: Message edited by: RageMachine ]