This plan would cost alot of money, because the batteries are not currently connected to the grid in a way that they can provide the power to the grid.

Batteries wear during charge/discharge, so putting this additional load on the batteries will require them to be replaced more often.

Batteries perform substantially worse when cold, so they will have to be heated somehow during the winter -- the power for which has to come from somewhere (e.g. the battery itself, which would put even more wear on it).

Researchers at the Lawrence Berkeley National Laboratory suggest that electric batteries installed on freight rail lines can be utilized to address spikes in energy demand, providing backup power during extreme weather events. By leveraging the existing infrastructure connecting trains to the power grid, the mobility of trains allows for flexibility in responding to weather fluctuations. The use of train batteries for backup power can potentially reduce the need for costly transmission lines and infrastructure upgrades. The study highlights the extensive rail network's capacity and its ability to carry weight, making it a viable option for cost-effective backup power. However, the researchers emphasize that power from railroads would still need to be supplemented by other sources, and the batteries can be relocated to different cities based on advance predictions of extreme weather events.