Where's here? The UK and most of Europe, for instance, still has plenty of diesel service.
I don't think I've ever seen a diesel train, ever. In fact, for a long time I was (blissfully) unaware of their existence and the fact that they do exist still surprises me...
Diesel engine driving electric motors (for torque and efficiency)
I think that's what parent meant.
Doubtful. Electric in EMU or in the context of Caltrain electrifying means pure electric traction power. In the United Kingdom I think they make some differentiation between a DMU (diesel-hydraulic, like an automobile with an automatic transmission) and DEMU (diesel-electric like a locomotive). There were diesel-hydraulic locomotives along the west mainline for a bit, but in general diesel-hydraulic locomotives were fairly uncommon.If it's being called electric it's not going to have a diesel engine of any sort.