Hi Robin,
The gate doors are open for Darnell and Couch. This graphic shows the approximate view of Darnell with the doors open and closed.

Excellent animation as per usual, James.
It highlights why Royell can't understand that the gates are wide open in the Martin film.
Towards the end of the clip below we see Sawyer, cigarette in hand, leading Brennan to his car where he briefly questions him.
For a second we see the gates in the closed position and I believe we also see the "citizen" that Mooney grabbed to make sure no-one went in or out.

I've watched this clip many times and get the impression that the gates have just been closed and the citizen is securing them (possibly)
We know from the photographic record the gates were wide open at 12:40pm (Hertz clock time)
I believe this actual moment can be pinpointed with some degree of accuracy.
After his conversation with Brennan, Sawyer contacts dispatch:

This transmission is timestamped 12:44pm
However, there is a slightly earlier transmission from Saywer.
At some point, just before a timestamp of 12:43pm, Sawyer contacts dispatch:
"We need some more men down at the Texas School Book Depository. We should have some on Main if we could get someone to pick up and bring them down here."
This transmission is made just before 12:43pm. We can assume Sawyer makes it as soon as he gets into his car and before he questions Brennan.
So we're looking at the closing of these gates around 12:41pm.
Exactly as you have marked in your animation.