I'm not sure that this qualifies as a "railroad festival" using the examples you've given, but the East Broad Top RR holds its annual 'community appreciation day' to coincide with the Orbisonia & Rockhill town festival. Within an easy walk from the RR station are craft and food booths, games and other family-oriented activities. Meanwhile at the EBT RR there are additional trains running, including a 6:30PM twilight train, as well as guided tours of the historic maintenance shops and other RR-related displays. This year's community appreciation day is Sat. August 18th.