Re: From the Battery University
"Where I live -- in the land of hydro-electric power* -- the overnight low temperatures are less than 5°C for 6 months a year."
Where you live, you have a house. Your house is connected to endless grid electric power. This electric power is connected to the electric car to recharge the battery. In other words, when the electric car is parked at your house, it has access to essentially unlimited electric power from the grid.
Why oh why oh why would the car designer fail to provide a grid powered electric heater for the battery pack?
See other post about how to combine good insulation around the battery to minimize heat loss, combined with some thermostatically controlled air ducts (doors) to provide unlimited cooling when appropriate.