The high level "handrails" are actually ice breakers as you suspected. Ice sickles form on the roof of the snow sheds on Donner Summit during the winter. The ice breakers knock them down. When the ice sickles get too big, they go in the tunnel and shoot them down with a shotgun. If that doesn't work, they cut notches in them and put explosive cord in the notches. Then they explode the cord.