Not train related, but I found
this article that discusses a drop-in transmission replacement for HMMWVs that allows them to function as 30 kW generators in addition to being usable as an ordinary vehicle, with similar systems under development for "larger trucks" to function as 30-125 kW generators depending on application and configuration.
Poking around on Leonardo DRS' site, the HMMWV power generation is 30 kW at 2000 RPM and 10 kW at engine idle, both 208 Vac. The "larger trucks" would be anything using an Allison 3000 or 4000 series transmission, which would include Strykers and MRAPs.
Even though it's a recently introduced item, I don't think it would be outlandish for it to have been developed earlier.