C18 had this at ORD last week as well. I believe it's only used for long haul 747 and 777 flights. Of course, the 747's are moving to SFO and ORD will be 777 for long haul (and 787 at some point). Maybe the 767 internationals are loaded here as well.

ORD can use those gates for 757 and 767 domestic flights as well but I don't think they use the zone boarding signs for those smaller aircraft.

-RM