Can you contact AI from train?

[SurvivorSean]

Just curious if you can actually contact the AI from the train.  I noticed when dispatching that every now and then the dispatch would say something about a track being clear in the main chat after a squelch on th radio.  I was stuck at a red signal for a few minutes tonight (wound up being a player DS but I didn't realize).  Just curious what the AI is saying when he clears a track on the main radio.

I totally understand the communication to the signal box as that is self explanatory.  But the main chat I'm curious about.

Thanks

Sean