Before the building codes were changed to six storeys there was much research done by FPInnovations, NRC, and a whole consortium. These buildings—there are tougher things in place—must have sprinklers, firewalls, and all kinds of safety precautions.
Wood is a flammable material, but if it's mitigated by buildings with sprinklers and done properly these will be safe buildings that are safer than a lot of currently existing three and four storeys that don't have that in place.