Since all of the mount related commands (like making them rest and stand) imply reigns are being used, I think hitched animals should be able to follow you in darkness, since you physically have ahold of their reigns are you're leading them.
I know could just mount the animal to get around this but, it often feels like much better RP to me to dismount and walk my animals through crouded areas in cities, thorny underbrush, ect ...
That's all.