It’s actually hilarious how wrongly confident you are. A 1w xmitter would be more than adequate to jam or spoof your GPS, from a significant range. A HackRF costs $330. A 1w amp for the approximate frequency range of GPS and GLONASS can be had for $30-60. And that’s for spoofing. GPS jammers that can be had for…

Sure they could, the same way that diesel-electric locomotives do, by running directly off of the generator, bypassing the batteries entirely (or only dipping into the batteries on heavy acceleration, if the demand can’t be met directly by the generator)