Hmm, I am surprised that they don't know. I think there are plenty of other people who do. RF effect from meteorite trails is a well-known phenomenon from radio (people were using it to bounce messages in the 30s)
Here are some people using it to track meteorites - very near the frequencies in question:
The necessary condition for bouncing a particular frequency is that the path lengths of the plasma are the right length (say, half a wave length or maybe 2ish meters) which seems entirely plausible as a distance associated with the width of the plasma trail. It would not be at all surprising if a tiny amount bounced back and forth like a cavity resonator, OR, reflected ambient signals that the telescope wouldn't have otherwise detected.
So it doesn't seem that mysterious.