Yeah, in Switzerland they are pretty uncommon for civil transportation, but very common for transportation of goods, considering that a lot of big companies have private rails connecting warehouses to the national network that, ofc these rails are w/o electric wires.
Yep yep. Just sayin', that's what else they'd be. :)
That said, for 250km/h and up, electric is pretty much standard for rolling stock. It's a bit less common to have the freight going through the same infrastructure be all mandated to be electric too though.
(Also now that I look more into it, it's unclear that it's mandated that the trains that go through the tunnel be electric. In fact, Swiss Railways just bought some new rolling stock for maintenance that's hybrid electric/diesel (uses electric only when overhead power works, diesel otherwise) which makes sense for maintenance, but likely means the tunnel is perfectly equipped to deal with diesel emissions from trains. In addition, before they completed the overhead work, in 2014 they announced that diesel trains could transit the tunnel. Not open publicly, but that the capability existed. Anyway. Interesting question whether they actually require all rolling stock transiting the tunnel to be electric, and if so, why. I'm guessing it just currently happens that all the scheduled trains traversing the tunnel are electric, so the poster said "all electric".)
Actually, having bothered to pay more attention this morning on the way in, I noticed that the engines that I assumed were diesel were in actual fact electric; I had just assumed diesel from the shape and behaviour.
So, disregard my blathering, I stand corrected (hopefully!)
me too, I travel regularly from Basel to Lugano, daily in the Bern - Zürich, also using regional trains and never saw a diesel machine for passengers transportation, except for some rare unexpected cases.
I traveled some times from Zürich to Munich and saw that in the German side, rails have no electricity and then the SBB are forced to use a diesel powered machine, but except for that, I still have to find a connection where the diesel machine is necessary every time, I am curious!
Actually, due to increasing traffing from Switzerland to Munich, Deutsch Bahn decided last year to upgrade and electrify the connection from Lindau up to ( I think ) Geltendorf.