iOS 6 Maps: Able to cache route or location offline?
Maps in iOS 6 should actually do a better job of this, because it uses vector based maps, which use far less data than the old image-based tiles, which means they can stay in memory longer, and more can be cached.

You can test this yourself by loading up Maps for an area, then turning on Airplane Mode and browsing around. In my own testing I found I could keep maps for most of Toronto, although when zooming down, it lacked street names for some of the smallest streets.

Searching or routing won't work without a connection, but any route or places you searched for prior to disconnecting should stay in place as long as you don't clear them.