Western Ave. is also the first METRA station stop on the Milwaukee District and where the two lines diverge (one to Fox Lake and the other to Geneva). I believe Amtrak follows the Fox Lake line at least through Glenview (it's 1st stop), but I'm not sure if/where it diverges on the Fox Lake line to get to Milwaukee.
Well, sort of. The MD lines diverge at MP 5.4, Pacific Junction, which is west of the Western Ave stop. There at Tower A5 the MD-N (Fox Lake) line is straight ahead (north) while the MD-W (Elgin, Big Timber) line curves to the left (west). The EB follows the MD-N.
The line that goes out to Geneva is actually the UP-W and it crosses the MD lines at Tower A2, just east of the Western Ave stop.
(Sorry for being nitpicky, this is basically my backyard.)