the underground access to the midfield terminals will occur in several stages. the first stage will include the opening of the pedestrian walkway from the main to terminal B. that pedestrian walkway will continue to the NEW
terminal C/D (remember that B is now 'permanent', while C and D are 'temporary'). rail will also go to C/D, but only after they are rebuilt.
the 'G' terminal for UAX is nothing fancy bcs it too is temporary - the new C/D terminal will be in that area - you can see that much of the expanded ramp area for those new terminals has been built already. i believe the new C/D will include express gates too.