Sort of. The Red Line is like that too, since it runs 24 hours.I am somewhat surprised that there were as many as 32 people around at 3 AM to be injured. Or, are the CTA trains like many of the "Night Owl" bus routes here in the San Francisco area that homeless people are allowed to use as "moving hotels" -- so long as they pay the regular fares?
There are also a lot of shift workers at O'Hare; though, I admit I don't know when the typical shift changes take place or when various crews need to report for duty.
Not to mention, some people who stay at the hotels near O'Hare take advantage of the free shuttle service. They take the Blue Line to the airport and then call for a shuttle.