I wonder if McPier is requesting this. I don't really see a huge call for this at the moment. Most conventioneers arrive in groups and get a coach to their hotels directly from the airport and then from the hotel to McCormick, possibly via the busway from the loop. The big local event there is the Auto Show and MED makes extra stops (and there are several bus routes at the west doors as it is) so an airport connection doesn't make sense for that, other than for NW suburbanites, though if 18th street could be a stop as well, Soldier Field events and the Museum Campus could be served.
At a more basic level to run express trains via the subway from O'Hare requires additional tracks and I'm not exactly sure how the connection between the red and blue lines was supposed to work - I think it just broke the four station long platform on the red line and through a tunnel over to the blue line or something like that. Equally fraught and complicated for Metra do to that too since there needs to be new track, probably in tunnel, to connect quickly (remnants of private companies having built the various stations and routes).
And we really have other more urgent transit needs around Chicago that should be done first (and if you are a doomsday person, the "looming pension crisis") and I don't see this happening without massive federal support. I hope this isn't a prelude to another push for the "third airport" in Peotone.
