Marty connecting Reggie to the gang was getting the info from the snitch he followed.
Marty is a cop. A veteran at that who lives in a car with all the traveling they have to do. He is a native of the area and listened to the scanner to connect the dots. As soon as they arrived and got out the car someone called the cops.
Also what gives you the idea they even mentioned the project raid to these new cops? From watching the interviews they never mention any of that stuff.
Sorry, I wasn't clear about the first point. I meant that the Reggie Ledoux working for a gang that Rust used to do undercover work with is a wild coincidence that really tests my suspension of disbelief. The info that Reggie Ledoux is the Iron Crusaders cook came from Marty.