On the consist:
Right now, the trains are four cars. Two locos is probably overkill for that (though it means there's one working if the other dies on you), but the plans are to have trains get up to about 8-9 cars (I don't think there are plans for the trains to be any longer). At that point, I think there's at least some case to be had that better acceleration is to be had with the second loco.
So they think that it will make sense in the future to more than double capacity on each train? Why not just run more four car trains?