[JudasGoat]

Spec sheet for the tug. https://www.crowley.com/wp-content/uploads/sites/7/2023/07/2... Edit. According to the specs, it has 2 onboard 300kw diesel generators for "long transit".

[Symbiote]

With 600kW of backup generators but 4200kW of electric motors, I think it's clear those generators aren't the main power source.

I have no idea how ports work, maybe tugs occasionally need to go between ports or something like that.