I did this with Tychus (recruit Vega first) but it might work with Vorazun? Mind control one of the units escorting the train by following along with it keeping pace with the train. Immediately order them to run forward, away from the train.
For most (all?) of the train’s life, this unit will keep disobeying orders and try to return to its position in the train escort formation even though the unit is mine now. It’s a tug-of-war against the in-game scripting still controlling the unit, and me trying to maintain control.