< InFAMOUS
Use your map to locate the buses. Do not approach them from ground level. You have to get above them and use Static Thrusters to glide down on the roof of each bus. This sounds a lot easier than it is, and there will be Dust Men running along with the buses. Their shots can knock you off course and bring you in range of the machine guns on the buses. If you do get knocked off, run for the nearest alley and find a relatively quiet spot to climb a building.
Once on the roof of a bus, target the engine in the rear of the bus and fill it full of electricity. This will shut down the bus. Once all four buses are destroyed, the mission is over.