Those are very specialized vehicles, that's most likely the reason they haven't been electrified yet, that will probably only happen as they age too much and can't be maintained anymore, mandating a complete, more modern replacement.
I also doubt they make up a substantial part of the rail traffic, if we go about it that way we there's a whole bunch of vehicles with horrible CO2 emissions that only have gotten barely viable electric alternatives in the last handful of years, like excavators, bulldozers and all kinds of other construction/hauling/maintenance vehicles.
There are electric (battery) versions of these vehicles for use in tunnels, where diesel fumes would be a problem. Much construction equipment is often converted roadbuilding equipment, and that's still diesel powered.
However, railway vehicles tend to last for decades, so it might take a long time for everything to be electric. The people buying them can both afford and have the expertise to purchase reliable, repairable equipment. It's then run on a perfectly smooth "road" without much rough handling.
I also doubt they make up a substantial part of the rail traffic, if we go about it that way we there's a whole bunch of vehicles with horrible CO2 emissions that only have gotten barely viable electric alternatives in the last handful of years, like excavators, bulldozers and all kinds of other construction/hauling/maintenance vehicles.