I don't think this makes sense. Rail freight is about 20x more expensive than transmission at current battery densities.

Transmission: $41.50 per MWh per 1,000 miles. https://docs.nrel.gov/docs/fy22osti/81662.pdf

Rail freight: $160 / ton per 1,000 miles. At 220 Wh/kg a ton of batteries is 200kWh. So rail costs $800 per MWh per 1,000 miles without considering the cost of the batteries themselves.