The M40 diesel - hydraulic had a relatively small engine, but it was used in the switch-yard for better acceleration under load than the larger diesel-electric engines, including the Sweedish-made imports. This was before 1990, mind you. https://en.wikipedia.org/wiki/List_of_Hungarian_locomotives#/...

Hydraulics is just oil under pressure, electricity will drive a pump just as good as diesel. The real problem for electrics on the job site is they use a lot of energy per-day so you're looking at very large batteries, or else (more realistic) swapping batteries during shift changes.