The rule of thumb is that any mountain railway that is going to a town is included in a GA/regular day card. These railways serve as a regular means of public transportation for the town residents, and as such are part of the 'regular' travel network. This is why you can get to Grindelwald, Wengen, Murren, Zermatt, etc. on a regular day pass without paying a supplement.

Mountain railways that only serve tourists aren't part of the national travel network, and exist to make money, which is why you will (almost) always have to fork out for them even if you have a GA or day card. Examples of such railways are the Jungfraujoh, Pilatus, Rigi and the Gornergrat.

Anyway. Just so ya know....