Tesla's motors run on 3-phase AC internally. (That's why the name of the company is "Tesla.") The trick would be finding a way to engage the internal inverter and then tap off it, possibly with a transformer to make it 120VAC. The conversion penalty of Tesla's internal inverter and your switching battery charger are going to be quite small.

I'd be a little surprised if the new truck doesn't just have an outlet built-in.