The train does operate until closing, but as the crowds die down, they take a train or two off the tracks. So during the day, there may be 4 trains, but near closing there may be 2 trains.
When we were there end of Nov, there were two trains and they each made different stops until the fireworks were cleared out. I'm not sure if the train runs during the fireworks, but I do know they said Toontown Station was closed for the first couple of rounds.
We were in the Main Street Train Station during the snow after Believe (fireworks) and it was a good 15 minutes before the train pulled into the station, then we got off in ToonTown to ride Small world and got back to the Toontown station at 10:30, the train didn't pull in unitl a few minutes before 11:00.
Something we found out also, once it is closing time, the train makes one more round trip, but exit is only allowed at Main Street. So if you left the stroller at Toontown and figured you would hop on the train to go get it, after closing time YOU are not allowed off the train. The train CM had to go get a families stroller and tell her how to break it down. They could not step one foot off the train.