It's UP's railroad. Including the bridge. Nothing has been said in public about orders to replace the bridge - references would be appreciated for further research.

Amtrak is the contract passenger train operator for the Capitol Corridor JPA, with major funding from the state via Caltrans. There are also a couple of long-distance Amtrak trains. All pay UP for use of their line.

The state did pay for many improvements to make passenger service beyond a couple of long-distance trains a day possible. A major one was restoring double track between Davis and Sacramento across the Yolo Bypass (SP had removed one of the tracks during its declining years). Plus of course all the new and reconstructed stations. And much of the equipment for the Capitol Corridor trains. But even with all of that, it's still UP's railroad.