Game won't let you begin this mission until you don't destroy the Mobile Command Centre in Lantern District. The latter is described in the City chapter. I recommend to take control over this or other District whatsoever, so you unlock the quick travel option between northern and southern part of Seattle.
Approach the marker in the northern part of the Lantern District and begin from listening to Eugene, who is a big fan of Delsin. After the conversation, head for the Waterfront. But, simultaneously, be careful because there is a DUP Force base nearby. When you get to the place, notice the steel supports of the highway. Start aiming at the supports (screen above) and destroy them with distance attacks - even the simplest powers of Delsin are ok.
Wait for the cut scene showing arrival of the convoy and collapsing of the road. When you regain control, head for the convoy and start attacking DUP soldiers gathered around. Here you should use the Smoke power, because you can easily regenerate it by sucking the power from vehicles. Ignore the helicopter which may appear over the highway - Delsin won't be attacked by it.
Move forward slowly and don't hurry, because you'll run also at enemies with powerful powers. Remember to cover when Delsin gets hurt more seriously and draining the smoke from wrecks so you can use the better attacks and heavy ammo (Cinder Missile power). When you get to the prison buses, approach one of it and check it (press the touchpad). It launches the new cut-scene with helicopter landing on.
When Delsin regains consciousness, listen to the conversation with Eugene. It concerns using the tracking device. Now it's good to switch onto Neon category, as you'll benefit from the Light Speed power to get quickly onto roofs. When you are on one, launch the tracking device and set the direction of movement (screen above). You don't have to listen to all DUP agents' conversations and have the number chosen for the all time. Remember to move in a straight line and launch the tracking thing from time to time, to make sure, that you run in a right direction.
Tracking device will take you to the eastern part of the city, between the Lantern District and the Rainier. Here you find a first prison bus wreck. As there are enemy soldiers nearby, it's recommended to attack from the air. During the encounter be careful and aware of enemies who can use power to destroy barricades. Attack them from sides and destroy their covers.
After securing the vicinity, approach the wreck and search it by pressing the touchpad. This will make well armored enemies to appear here. If you didn't take over the southern districts of Seattle, that'll be your first meeting with them. Try to keep them at bay, because you have no chances at the short distance. Avoid also their strongest attacks - kind of a shockwaves (use covers or jump over it). To eliminate them, you should use the best distance power and deal with them one after another.
After cleaning the vicinity, get onto the roof of any building and use the tracking device again. Application will lead Delsin to the second bus wreck in the southern west part of the Rainier. This time, you can be relaxed, you won't be attacked. Check the bus (touchpad). You won't find here anything.
Use the tracking device for the last time. It takes you to the third bus wreck in the eastern part of the Waterfront. As you probably noticed already, DUP is fighting angels here. You don't have to attack angels (but it's possible, each hit makes them disappear), because they are no danger for Delsin and they may be even helpful at eliminating enemy soldiers. Focus on DUP troops and, again, beware of the armored enemies, who are not easy to defeat. You have to eliminate all enemy characters and search the last bus (press touchpad). This mission ends and you get an access to another one - Reggie takes Flight.