Because they live on an island with limited resources, the D-vil denizens don't use fire (and be extension, wood) to light the streets at night. They use glowing fishes.
See, somewhere along the line, some type of fish suffered a genetic mutation that made them glow. D-vil fisherman started catching a bunch of them, which eventually led to them being strung up in fishbowl lanterns between the buildings in Tenement Square. Presently, the glow fish are farmed off the coast, because the actual wild population is (predictably)...floundering. :P