I'm back from my trip! I actually came back on Monday, but today was my first chance to post here.
I did as everyone suggested and I just scanned the AAR frequencies. I found a lot of activity in the New Carrollton, Union Station (DC), Penn Station and Philly yards. Along the trip, we made many stops and I did hear a lot of chatter in during the stops, but I didn't make notes at the various stops, so I'm sorry that I can't be more help to confirm those. I do remember channel 14 was being used quite a bit.
We rode a Superliner from Union Station to Pittsburgh and there was plenty of inter-train activity to listen to. It was mostly head end talking to the rest of the train (at least that is what I think it was). I kept hearing chatter like "Give me another sixty seconds." I think he was asking central control for more time through a switch. As much as I love railroading and modeling railroads, I actually know very little about operations. I guess I was hoping to get a little more understanding about how they operate from this trip
The ride from Pittsburgh to Philly was not a Superliner and I noticed we didn't have the same inter-train chatter, so I didn't do as much listening during the trip. I tried to listen when we were coming up on a stop. There was some chatter at the stops, but most were so short, they were very brief, if any.
I plan to take another trip later this year. I'll be better prepared to make notes on this next trip.