Something must've happened to the story because I can't find it anywhere in London on my part. The only recording of a Madison County test on YouTube that I know of is the RSH-10 in Mount Sterling going off in attack. There are two videos of it, one from 7/19/2013 (a Friday) and the other from 7/2/2014 (a Wednesday). I may try to message the EMA at some point to see when they test their sirens.
I personally don't think the analog ESC-864 on the McCoy Park 4004 came from the McCord Park 3000, as that one was updated with an ESC-2030 back in 2014 during the phase of when the county was upgrading the controllers on their old 3000's. I suspect that the county completely forgot about the Minerva Park 3000, so when they finally realized that one still had its analog controller they just swapped the boards of that one and the McCoy Park 4004 in either 2017 or 2018 instead of buying another new 2030 board. But who knows, I could be wrong about that.
As for Merlin Drive, it was first heard with a dual tone analog ESC-864 in July 2015 when I first recorded the Westerville Fire Department unit (which also has an analog). Before then, the Whetstone Park unit was last recorded in July 2014, and wasn't recorded again until three years later when it had already gotten updated with an ESC-2030 controller. The three units in Westerville with analog controllers all have the newer style 4004 head, which didn't come out until around 1998, and the ESC-864 was switched to digital in 1992 iirc. This leads me to believe that either those units had their heads replaced at some point, or they originally had a newer controller but eventually ended up getting retrofitted with analog ESC-864 boards for whatever reason (which I think is the more likely case). But again, I can't confirm this for sure, so I could very well be wrong.
Oh, I just remembered this. At one point, there was a second dual tone analog unit in the county besides Whetstone Park. In an old video of the McCoy Park unit (back when it had a digital 864), a dual tone Whelen can be heard winding down shortly after the McCoy Park siren winds down on both cycles. That was suspected to be coming from either the 3000 on Greenlawn Ave & S Front St, or the 3000 at Buckeye Middle School. Unfortunately, both of those weren't recorded until after they had gotten updated with ESC-2030's. If Merlin Drive and Whetstone Park did in fact have dual tone analog's at the same time at one point, then it's possible that the analog on Merlin Drive may have came from the one heard at McCoy Park.
Here's the link to the video I was referring to of the McCoy Park unit: https://www.youtube.com/watch?v=Y4a-TjtF3VA