Nothing places Tatum at the scene when the shooting took place besides his own mouth, but the same can be said of Benavides. This is covered in detail in the long "The Tippit Case in the New Millenium" thread.
It's unclear if the author regards 410 E 10th St as a hastily prepared ambush site, or a place where coincidentally the cop, the cop killer and the cop car in the alley all happened to converge. No mention of the last but he accepts at least part of what Holan had to say, curiously omitting the main point of her account.
In the same Drenas article that mentions the Andrews encounter there is another tantalizing Pulte anecdote.
Dallas radio personality Kevin McCarthy had a number of talk shows dealing with the assassination in the late 1980s and early 1990s. Bill Pulte heard this broadcast and repeated the following to me from memory.
A man called into the radio program and told this story. "My girlfriend told me something that might be important about the Tippit murder. She was driving east on 10th Street behind a police car; she was some distance behind it. The officer in the police car hit his brakes quickly and backed the car up very fast. The woman hit her brakes but could not stop completely and bumped the rear of the police car. She said "Oh no" to herself because she hit the police car and thought that the officer was going to be upset and give her a ticket, but the officer did not pay any attention to her. She backed up went around the police car and drove on her way. Later she recalled that the location where this happened was exactly where Tippit's car was when he was killed, and she realized that she had bumped Tippit's car."
Bill Pulte said that "the caller sounded excited and completely unrehearsed, and the call seemed spontaneous" The caller said that his girlfriend refused to come forward with her story because she did not want to get involved.
I don't think many take this seriously but what rings true is the part about Tippit throwing the car into reverse and backing up quickly, as if he had suddenly observed the patrol car in the alley. Incidentally, the attached view of #10's rear shows a small dent to the right of the "E" in "GALAXIE," although it looks more inside out than outside in.
Putting that aside, the larger question of ambush orchestration is not addressed. A tough nut to crack, I wish the author had something to say about this. It may be bad form to complain about the absence of something from an article, but this issue cuts to the heart of Tippit's murder.