I have read about the Mococco line reactivation here for some time but never scrutinized the situation.
On Google maps you can followed the line from where it joins the BNSF in Pittsburgh,CA.
Google's maps are pretty close to scale. Looks like Antioch did not allow residential property
For a good 300' from the right of way. That is good planning.
But Oakley & Brentwood permitted residential streets right up to the right-of-way.
Where ever I see residences very close to the ROW + grade crossings that will be the worst
conflict. It is one thing to have a train pass by.
It is another thing to have that train tooting the crossings.

I have attended zoning board meetings in numerous cities and towns. The developers
bring a lot of new property tax revenue to the table. The zoning boards are chartered with only allowing developments that are prudent and harmonize with existing permitted uses.
The railroads must be the second oldest land use in this country. (Agriculture being first).

About the only mitigation I see for these home owners is if they can get someone to pay for grade crossing improvements. If they can get some agency to fund quad gates etc. maybe they can get quiet zone designation and loose the 110db. horns.
People that sleep in a bedroom 50' from tracks and near a grade crossing have a real situation.
Example: Condos at 65th St. in Emeryville right on the SP main. (I still call it the SP)

Cal-P