I just know this by what I see when I go through Union Catching the trains. I may be right or wrong about the track assigments. Track assigments can change without proper or no notice at all.
Southwest service:(South Concourse)
6:26am, 7:15am, 8:35am leaves out of track 28
10:35am through the 11:40pm leaves out of 14
May be one rush train leave out on track 8 or 10, not sure.
Hertiage Corridor:(South Concourse)
All 3 depart from track 16
Off peak, and most weekend trains depart off of track 8
Milwaukee Dist.:(North Concourse)
West off-peak & most weekend trains leave from either tracks 5 or 7
North: off peak & weekend leaves from either 9 or 11
Most trains off of track 15