If you want to haul a large, heavy trailer long distances, diesel is still king. Not screwing around stopping every hour to charge, engine braking....this makes no sense.
Electric-diesel is king
Yes, although in the case of a diesel electric locomotive, the electric part is mostly for transmission driveline purposes, rather than efficiency. The load on the diesel engines at any given time is commensurate to the load on the electric motors, and hence the generator.
Unlike, say a BEV with Range extender, like the Chevy Volt or the BMW i3, where the load on the gasoline engine can be relatively constant, while the load on the electric motors is constantly varying.