The point is though, that the reports of this mux on AMC-16 at 85 cannot be correct, because there is no vertical transponder at the reported freq, and a signal at the freq/SR reported just isn't possible. The reports are almost certainly wrong, either they have the polarity wrong, or they are seeing the wrong satellite, or some other error. Since the parameters are exactly the same as the same signal on G25 at 93, I think whoever first reported this finding was seeing the wrong satellite, either aimed at the wrong sat, or perhaps had side lobes bad enough that they were picking up signals from 93 while aimed at 85. On a couple occasions, when my feedhorn wasn't at the right FL, I have gotten strong locks from transponders 6 deg away from where I was aiming, so it is possible.
However the fact that more than one person reported this on different groups suggests that some people didn't really observe the signal, but rather copied the info.