The very same talking points also works against battery-charging stations that are inevitably needed for battery charging trains, unless of course the plan is to just keep using diesels. Which is quite likely - it's quite possible Fairmount is being set up to fail with its enormous cost blowout, and the locomotive order for 10 battery locomotives also comes with 10 diesel locomotives and the option for 50 diesel locomotives attached. It's hard to not see the 10 battery locomotives as political cover to order 60 diesel locomotives.
If you walk over to the newly built North Cambridge battery-electric bus garage (elevation 13 feet above sea level), their transformers are clearly grounded mounted: