The FHP was on I-75 using the new overpass between corkscrew and Alico to target north-bound traffic after they went under the overpass.
There is no access to 75 from this overpass, so it could lead drivers to think there is no threat of LEO's using it to monitor I-75. But in this case they had a few chase cars and must have been calling people in.
One note; The shooter was shooting his PLIII through a chain link fence. I am sure they were getting readings because they had one guy pulled over, but I don't know if this method is "authorized" for speed readings.