That page says they use fractal algorithms, which would imply to me much smaller memory and storage requirements than a faithful recreation of real maps.

Honestly, to me a completely faithful representation isn't necessary. I want to learn to drive a car, or enjoy a very realistic car driving experience in simulated traffic. While having a one-to-one representation of the world would be great, it's not strictly necessary for that goal. To that end, car physics, different driving condidtions caused by weather and surface, and realistic modelling of traffic charachteristics (including law enforcement and the odd drunk driver) is far more important to me.

(But ummm.... Right now I just want to say sorry for hijacking this flight sim thread with car sim posts... :p I never thought it would get this much traction. No pun intended.)