Makes sense then. If it is DMR, do they receive analog as well? (Know nothing about DMR or digital radios in general)
They might be able to hear analog if their radio is set up to do this. I haven't noticed any dual mode settings in my 6x2, I don't know if others might have it.
Let's give a couple of examples.
1. If they were nearby using simplex and you were listening to their conversation you most likely would be able to talk to them. You would have to find out which talk group, slot, and color code they were using to do this. If they were on a repeater, you could work them on the output if the repeater wasn't transmitting.
2. If you've checked every slot and color code and still can't hear anything, then they're either using encryption or it's not DMR at all.
Since the signal is on the air 24/7, then it's most likely a control channel for a trunk system. The strange thing is that it's showing up on an FRS channel, which would lead me to believe you're hearing an image. Check ~10.7 mhz either side of the FRS channel and you might hear the same thing.
Jason