All they did was bring in a host of emergency vehicles, painted in Miami colors and logos. They set up a tent, a few bulletin boards, a lot of uniformed extras, and they were ready to roll.
This parking lot is right across the street (kitty-corner) from the tower they used as the Transcorp Building.
And they shot the scene of Travis walking with the kidnapped Harrison on the sidewalk that runs along this parking lot's eastern edge.
The aerial photo below was shot during filming by Rick's brother, Jeff, from the Comerica building:
I shot the photos below, also during filming:
(The camera is looking north from 1st Street.)
[ Click on the photos to see larger versions ]



Q.
How the heck did you figure out where it was?
A. In previous seasons, I've
usually had to hunt down the locations after viewing the episodes,
using clues from the various scenes. By the 6th season, though,
I'd developed a small group of fans, spies & tipsters who kept an
eye out for Dexter filming in their neighborhoods, and would let me know
in advance when something was about to film there.
Between those reports, my own personal reconnaissance around town, and a
few new resources I discovered, by the time the first episode aired, I
already knew most (but not all) of the filming locations, and only
needed to watch the episodes and match up the scenes with the correct
locations.
This group of helpful fans includes Kerry, Rick, Ellen, Susan, Jason,
Elaine, Joel, Julie, Geoff, Jeff, Jen, and others. My thanks to all of
them.
Rick first
alerted me that they would be filming here. So I drove past and
shot photos of the action. Later, several fans reported back to me
on the action.
And, as luck would have it, Rick's brother, Jeff,
works at the Comerica building, watched some of the filming, and got
the photo you see above of the police command center. (Small world, isn't it?)
According to Jeff, several of
the floors of the Comerica building are occupied by the INS (
Immigration and Naturalization Service), so there were numerous armed
agents working there during the filming. As it turned out, many of them
were invited and used as extras in the parking lot/command center
scene. (Thanks, Jeff!)