The day we can have generator-motor drivetrains like locomotives, is the day this diesel vs gas hp vs torque argument will end.
Beauty of a generator: it doesn't care HOW you generate the hp, 1 hp is 1 hp.
Turbines with no torque and 30,000 rpm, windmills with earth turning torque and no rpm, gas, diesel, nuclear reactor, you name a power source, and it has powered a generator at one time or another.
In the end, your towing power solely depends on your traction motors at each wheel / axle, and it only needs hp fed to it (in the form of amps and voltage).