User blog comment:Stormwell/Thoughts on Technology/@comment-1500935-20140210135550/@comment-3525200-20140210184219

Yeah, I suspect it's a local PA system which would make sense for a fortress.

Regarding the railways, I suspect that there probably would be coal-fired steam locomotives on the city-to-city lines. Whale oil seems to be used up too quickly for it to be practical and two rails are easier and cheap to both build and maintain than Dunwall's four rail system.