I had not realized that Cisalpina becomes a fully playable region with Gallia Togata, which includes allowing movement of troops. This came unexpected to me (I don't see any real hint to that in the rules or the card description), so I thought I would share the information as it may not be obvious to everyone!
The quote below appears in the comment to this post:
The unshaded Gallia Togata Event turns Cisalpina from non-playable into a Region. That makes all rules regarding Regions apply to it, except where the Togata Event text explicitly says something else. Nothing in the Event text prevents the Romans from Marching into or through Cisalpina.