Fire hazard depends on what type of Li-Ion batteries are used - or even if they're Li at all. As an article about the Moss Landing fire pointed out, the facility that burned was a very early battery plant, built quickly using a lot of shortcuts, and using essentially EV-type (NCA, NMA) batteries which are the least stable and most flammable type. The PG&E plant next door to it, only a little newer, kept working right through the fire, though it also had a couple of small fires (controlled quickly by fire suppression built in to the project, and using containerized batteries that are designed to isolate any fires that do occur) in the past. Modern battery storage uses Li-Fe-Phosphate batteries that are less energy-dense, but much less likely to catch fire because they don't use the flammable electrolyte found in the older EV-type batteries; you just need more of them for a given storage capacity. Then, there are other chemistries coming into use that are essentially non-flammable, like the flow battery SMUD is working on. So from a technical standpoint the trains could probably be made to work. Whether they would work well enough to be worthwhile (and profitable - it is freight after all) is a bigger question. And of course what chemistry is used is a subtle point that would escape most NIMBYs.