I would think that a city's statues could be considered "facts," and so not be copyrightable. You'd be taking statements about which streets are one-way in textual form, and transforming that knowledge into data on OSM. It's not like you're copying from another map.

I also expect that I'm wrong for various legal reasons which contravene common sense. Asking permission just seems like a safe thing to do, to be totally sure they can't turn around later and demand that the info be removed.