Hi Cecilia,
Currently, the Walt Disney World Railroad is not one of the attractions open during either the Morning or Evening Extra Magic Hours at the Magic Kingdom. At present, the rides that are open include:
Mornings:
Buzz Lightyear's Space Ranger Spin, Cinderella's Golden Carrousel, Dumbo the Flying Elephant, "it's a small world", The Many Adventures of Winnie the Pooh, Mickey's PhilharMagic, Peter Pan's Flight, Space Mountain, Stitch's Great Escape!, Tomorrowland Indy Speedway
Evenings:
Includes attractions listed above and Big Thunder Mountain Railroad, The Haunted Mansion, The Magic Carpets of Aladdin, Splash Mountain
Have a great trip!