Correct. Modern locos basically receive AC, convert it to DC, then convert it back to AC for the traction motors. Whether they receive AC through a pantograph,

Correct. Modern locos basically receive AC, convert it to DC, then convert it back to AC for the traction motors. Whether they receive AC through a pantograph, or a self-contained engine + generator, doesn’t really make a whole lot of difference. The power generation is fundamentally the same as in marine purposes, too. In fact, the modern engines such as the EMD 710 or GE 7FDL, often come in non-mobile stationary/marine operation configurations for these purposes.