To add some confusion to the question, I will give you some facts. I don't know how these facts will influence trains and traction.
- Gradients within Switzerland are partly steeper than in Germany and Italy, thus not every train that can be hauled by single locomotive in the neighbouring countries can do so in Switzerland.
- Maximum train length within Switzerland was increased to 750 m and trains of more than 500 m will get a discount on the track access fee when crossing Switzerland. Two trains arriving in Chiasso would have to go South as three trains.
- Trains crossing Switzerland with two locmotives get a discount on the track access fee, because their acceleration is better, which reduces the time a train blocks a block.
- Trains over the Ceneri can not normally go with one single locomotive.
Now you can speculate about the consequences. And I'm sure the railway undertakings will not do what you think ... :-P