There is a bunch of
stuff up on the CREATE page about the Grand Crossing rail connection project, including diagrams of the alternatives.
For the southern half of the project, there are two alternatives. One which seems sort of like a baseline alternative would would use the NKP flyover of the CN/IC and add a single track between the NS line and the Skyway. The other alternative does both of the things mentioned above plus includes several more new tracks north of the NS right of way where the NKP used to be and where Con Ed has some power lines.
For the northern half, one alternative would hug the east side of the NS ROW adding a track there as far north as 42nd St. The other alternative would build a new connection from the NS line to the Metra SWS line through Englewood from roughly 61st & Stewart to 59th & Wallace and utilize the Metra line from there.