Hello swissbio
The GA grants you free access to all these trains except Jungfraujoch. The Gotthard Panorama Express is not running in winter, though.
When you look up schedules on www.sbb.ch/en, you will find panoramic trains marked as PE on the timetable. For Bernina Express, Gotthard Panorama Express, Golden Pass Line, Jungfraujoch, and Voralpen-Express, there are regular trains running on these lines, too.
Other beautiful lines are Chemin de fer du Jura, Train de Vignes, Rocher de Nayes, Mont-Blanc Express, Mt. Rigi railways, Mt. Pilatus cogwheel train, but, in fact, there are many more. You can find more information on each single train by using Google. There are excellent websites available. My absolute favorite in winter is Bernina Express (Chur-Tirano). Take a stop at “Alp Grüm” station for lunch.
I suggest to check the GA validity map (see Downloads box) to understand the area of validity of your GA (same map applies for GA Duo Partner). Then, once you have chosen a train, it might be a good idea to visit a SBB travel centre. The colleagues there can answer specific questions on the train as well provide you the timetable. Alternatively, you can ask the colleagues at the SBB contact center: Phone 0848 44 66 88 (CHF 0.08/Min.)
Best regards,
Roland