It's been almost 20 years since the last time I was there but at that time the ex-SP tracks out of Tracy ended at the San Joaquin county line. I have heard two stories of why that is the case.

1. Alameda County charges property tax on railroad rights of way. By officially abandoning the ROW and pulling up the tracks the SP didn't have to pay the tax anymore. This is a believable story since the tracks stop exactly at the county line.

2. Alameda County officially owns the ROW. SP was just clearing their track off it. This is slightly less believable because of the track stopping at the county line. Why wouldn't they have torn up more of the track since they had the crews there?

One of the proposed changes to the ACE train route would reroute it to this line from Midway east. This would take the ACE train to Tracy's downtown transit center. This seems like a good plan. It would get ACE off a big portion of the UP and make the ACE station more convenient to the Tracy commuters.