Trains used any more?

The Baltimore Orioles play their home games in Oriole Park at Camden Yards, which on Google Maps appears to be adjacent to the Transportation Center at Camden Yards.

https://www.google.com/maps/place/Transportation+Center+at+Camden+Yards/@39.2983009,-76.6194262,15z/data=!4m2!3m1!1s0x89c8035e7325b6e1:0xabcc9d8d5eb31685

Amtrak train 511 type GE Dash 8-32BWH 4/14/10 by Leo W. Persick, Jr. Wikimedia Commons

Not far to the north is the Baltimore Penn Station, which runs Amtrak trains. Train travel in the northeast corridor is pretty convenient on these Amtrak trains among places like Washington, DC, Philadelphia, New York and Boston.

How often are trains used, especially by the Orioles, Nationals, Phillies, Yankees, Mets, Red Sox?

Midwest locations could also use trains. The Colorado Rockies are in Denver and isolated. Only a little less so are the Mariners in Seattle. But even many of the western teams are close enough to use trains.