Do iOS 6 maps include public transit information and routing?
As of right now, no, the new Maps app lacks transit directions. Instead, when you select Public Transit as your travel mode, it pops up a list of installed (or available from the App Store) apps that can provide local transit directions.

And, as of right now, no, there is no Google Maps app in the App Store (though you can still use Google Maps effectively from Mobile Safari). 

There not much to do but conjecture as to why the Apple-made Maps app doesn't include transit. From Dan Moren's excellent iOS 6 review at MacWorld:


  This is an odd solution for Apple, which usually prides itself on
  providing a consistent experience. But I suspect that handling public
  transit directions simply wasn’t an option for Apple at this point,
  and if it came down to offering a third-party experience versus no
  feature at all, Apple opted to not leave its users completely
  high-and-dry.