Grapple all the way to the top of the building across from the Urbarail Station to find this.
Check the skyscraper across the street from the previous trophy to find a wood panel. Use Explosive Gel or a glide kick to get through it - there's a trophy on the other side.
Check around the same building at street level to find a green hook. Grab it with Batmobile winch and rip away the shutter to find a trophy inside. When you do, a sentry gun will pop up, so switch to the Batmobile remote controls to destroy it.
Grand Avenue Tunnels
You can get this while completing the story missions. When you go into the tunnels to search for the Arkham Knight, look for this on a ledge when you first encounter a room with militia repairing some drones.
Grand Avenue Urbarail Station
Midway up the station is an area where you fought the Militia earlier in the story (or soon will). Look for a wood panel and punch through it to find a trophy on the other side.