Interesting comments on train. I have no clue as to what is right.

On one hand, I would guess a lot of traffic from BA to Rosario to Cordoba. But not too much beyond. And Mar de Plata is a 3-4 month busy period. And I would think right of way is fairly cheap at this time.

On the other hand, not much traffic once 20 miles from downtown BA. Roads are not great, but not too bad and the traffic is minimal. Sure an expressway would reduce travel time 25% or so - mainly by bypassing infrequent towns. But rare traffic jams, etc. in my experiences.

However, train traffic will likely increase in a country with hardly any routes, if they put in a better system. And might as well go with high speed as distances are far and land is pretty flat.