Let's see. 240V @ 40A would take about 8 hours to charge a Bolt. That's three Bolts per day. To get to 12, each Bolt only gets a 25% boost.It won't be too long before we see tow trucks with built-in, V2V charging capabilities.
It is mobile devices like this, though, that make me wonder why businesses can't just install low-cost DC-DC chargers run off of batteries linked to their local power supply. Even a 250 kWh battery bank with a basic 240 V @ 40 A power hook up would be able to charge 10 to 12 EVs per day.
Put another way, 240V @ 40A = 9.6kW. Assuming 90% efficient, it would take about 29 hours to charge the battery bank.
This setup would only be good for a convenient boost. How much would you pay for a 25% boost? There would have to be a whole lot more EVs on the road for this to make economic sense for a business. If someone did this today, it would only be to make a statement.