Chicago TRACON feeder is now listed as four positions (NE, NW, SE, SW) rather than the old east and west.
When did this change?
May I assume that each of the four is responsible for a single arrival post (the old CUBBS, etc.)?
More than likely. They could have adopted the concept of the "4 Corners Post" plan that L30 (Las Vegas TRACON) adopted roughly 13 years ago when they implemented RNAV procedures. Basically, each position has their own entry and exit gate into the TRACON area, and are responsible for feeding it to the final controller for sequencing.
That makes absolute sense when you look at the BENKY2, BULLZ6, and basically all of the RNAV arrivals into KORD. This also makes changing configurations much easier as well.