They didn’t dare risk the optics of an all EV failing when it was needed to respond to a fire.
Even if the battery gets the firetruck to the scene, I’d think the energy draw for pumps, lights, hydraulics, fans etc. is absolutely massive.
Sorry, can’t use the Jaws of Life to extricate you until we recharge. Keep your finger in that arterial bleed for another half hour, would ya?