I think PS would be fine, although it's been a while since PS6 so I don't really know how techniques translate from CS3. For example, Bevelling is a Layer Effect now, but it seems like it was a Filter in PS6. Anyway, it seems like the logical start would be to block out the silhouette of the city as a solid shape, and erase lines through it to represent the streets as negative space (like so, for example).