MT-
I guess anything is possible.
AFAIK, no one has ever come forward and said, "I was the guy who met DPD officer Joe Smith near the GK. I carry a federal badge that looks somewhat like a Secret Service credential-badge."
It is possible the railroad dicks simply did not follow the JFKA case, and thus did not know they had been a source of confusion.
This seems somewhat the case of Secret Service Paul Landis. A couple years back, Landis wrote a book that said he found a slug that looked like CE-399 in the presidential limo, and then put it on a stretcher in Parkland Hospital. There is an 11/23 FBI memo to the effect that Secret Service agent had found a slug in the limo, giving the Landis tale some credibility.
In the intervening years after 1963, Landis seemed to put the JFKA largely out his mind.
Powell, from the Army 112th Counter Intelligence Corps Group, was carrying a 1960s-era camera on 11/22, which were usually bulky. I wonder if Powell carried the camera with a strap around his neck, which was common in those days. Powell seems like a long-shot to be the ersatz Secret Service man on the GK.
Neither Weitzman or Smith mentioned a camera.