anyone ever take part in this?

I did - many times.  Before, and while, the plaque was there.

We simply waited at the plaque (or prior to its installation, at a designated gathering spot, usually around the gift shop) and then a park rep (most often someone in Guest Services or occasionally PR/Marketing) would walk us back to The Beast prior to the rope drop.  Prior to her retirement, Ruth Voss did oversaw the walkback most often.  She's the one that invented it, of course, waaaaay back in/around 1980.  After she passed away, some ACE members actually referred to it as "The Ruth walkback" and would all reminisce about her.

Sometimes, we'd arrive at The Beast before morning tests were done by crew, so they'd hold us at the ramp that leads up to the station.  Sometimes they'd hold you until after the National Anthem played (I think...) When the ride ops gave the thumbs up, ACE members rode.  Sometimes we'd get 1 ride, others 2 or 3... it just depended on the timing.

It was always amusing to see the faces of all the teens/kids that raced back to Beast after the rope drop.... only to find they were NOT the first there.  "How'd they get there so fast?" 

Here's a picture I took of a few of my closest park friends (Reids and "Sparky"), while waiting for the walkback.

FYI - I found this to be one of the absolute best ways to get to meet other "enthusiasts." There are countless people I know today because I met them while waiting "At the ACE plaque."  I really miss it for that reason.  CF did away with it, attributing it to the Platinum Pass early rides.  Its really a shame they made that decision... it was always a testament to the strong relationship KI & ACE used to have.

Also, I met a great deal of ACE members when I was on The Beast crew and worked open shift.  Obviously we'd have to get there A LOT earlier than the other ride crews, but it was always a fun start to the day.

FYI - the plaque still exists to this day... but no longer on International Street ;-)