[orulz]

How much of those yards are Amtrak and how much are Metra?

With functional through tracks at Union Station you wouldn't need as much storage so close. Every BNSF train could run through onto MD lines, and vice versa, meaning no more Metra storage needed in the West Loop.

All inbound BNSF trains could continue through to the existing Western Avenue station on the MD lines, stopping at a new Fulton Market station along the way. Some would terminate and turn there, or lay over at Western Avenue yard, while others could continue out to the end of the line.

In the opposite direction, all MD/NCS trains could continue through to Western Ave on the BNSF, stopping along the way at Halsted and a new station near Paulina for a transfer to the Pink line or a walk to Illinois Medical District. Again, some trains could terminate/lay over, while others could continue on to the end of the line.

This would benefit riders, because you both wind up increasing off peak frequency on the in-town portions of these Metra lines, and because in both cases you wind up serving a significant and growing job cluster (Fulton Market and Illinois Medical).

Anyway, this wouldn't move Amtrak, but it does move Metra. I would not, however, recommend using this land for a baseball stadium. Having office and residential development in this area would be way more valuable.