Outside of being able to build diagonal roads at the proper angles, the most difficult thing about recreating the Bay Area road system on an accurate map will be forcing SC4 to not put in tunnels. Also, while I'm sure RH will make it easier to create a more realistis San Francisco, I doubt they will have the roads build stairs, as opposed to sidewalks, when building on an angle (can you imagine Sims walking up or down Lombard or Telegraph, the people in wheel chairs would be hilarious).