You will receive a transmission of a distress beacon near the GCPD. The flare is just south of the GCPD. Head up to the roof, take out the group on the helipad and then head inside to talk. Your mission is to take out the six Titan tanks around the city. They will all be marked on your map.
Industrial District - This container is west of the Steel Mill and it might be guarded by a few enemies, possibly armored. However it shouldn't pose any serious challenge.
Steel Mill - It's just inside the back door. Do the mini-stalker sequence outside and then walk in, turn left and it should be there.
Wonder Tower Foundation - This is the area with the big predator area that has the elevator shaft in the middle and leads to Wonder Tower. In this room, on one of the sides (east I believe) is the Titan Tank waiting for you to clear the room. Of course you could also skip clearing the room, blow it up and leave too.
Subway Tunnels - This tank is by the exit that leads to the Subway Terminal and is just beside the wall mural of Solomon Grundy.
Bowery - Just outside of the Subway, head east and then take a right (it will appear that you're in the southern section of the Subway Station but you are above it) and the Titan tank should be right there.
Museum - Go into the museum and head for the War Room. The Titan tank is in the Southwest corner of the room but you have to go around the right side and come behind the gate to get to it.
After you've found all of these, head back and talk to Bane. You'll be interrupted by a bunch of goons. Take them out but watch out for where Bane is because he can hit you if you jump in his way. Once the Thugs are out of the way, destroy the six remaining tanks of Titan. Mission complete.