Pokémon SoulSilver is a video game where you catch and train Pokémon. There are no "magnet train passes" in this game.
Magnet trains are a form of high-speed rail transportation that uses magnetic levitation. While there are real-life magnet trains, this is not a concept that exists in the world of Pokémon.
Perhaps you are thinking of the "Train Pass" item in Pokémon SoulSilver, which allows you to ride the train between towns. This pass is not earned in any specific way but is given to you as part of the story.
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