I can add a few more details and my experiences here:
The truck was a porta-potty service truck (not a semi, but that's a nit-pick) and the driver was killed. You can see some footage from the scene at this news report:
https://www.kion546.com/news/one-de...es-with-truck-south-of-castroville/1141971303
The crossing was a dirt road into fields, with no lighted crossing signals, and just off an intersection with a paved road that runs parallel to the tracks. I haven't seen any further details, but it would seem almost certain that this was unfortunate driver error, which as is so often the case, led to his death.
I was not on the train at the time; I was waiting for that train at Sacramento, where I had arrived on the California Zephyr earlier that day.
The station staff at Sacramento did as best they could to inform us, but it took time for information to come in about the magnitude of the damage and ensuing delay, so for some time, the expected arrival time just kept moving in 30-minute increments. I'm told that after the on-site investigation and some new engine crew arrived, they backed the train into Salinas, set aside the damaged engine, then eventually proceeded to Oakland, where a second engine was attached.
During the delay, the Sacramento station staff were awesome in trying to host us overnight as best as they could. Sacramento has a pseudo-first class lounge, but it's really just a small corner divided off by high office-cubicle-type dividers, with some couches and chairs, though these at least had cushions unlike the wooden benches in the rest of the station. And had one forlorn outlet strip duct-taped to a table. They brought in pastries, fruits, etc in the wee hours of the morning, and then later fried chicken and potato salad for an early lunch. The staff were super friendly and accommodating, absolutely doing their best.
We got underway almost exactly 12 hours delayed. On the plus side, it was daylight while going through the very scenic regions south of Mt Shasta.
I was very disappointed at one conductor in the southern Oregon area who came through the lounge car and thought it appropriate to make several tasteless jokes at the dead man's expense. He seemed to think he was quite the comedian; I thought it totally unprofessional behavior to be sure. I wish I had got his name to report him. At the time, I was not brave enough to call him out - he struck me as the power-tripping type who would probably toss anyone who challenged him off the train just because he could.
To get the equipment back on schedule, they terminated and turned the train at Portland, where we arrived at about 3:50am. Again, the station staff there were excellent at getting everyone directed to the appropriate bus connections, at a time in the morning when there is not usually any activity there. Rather than doing 'local' service where the busses follow the route, stopping at each station stop, they did direct busses to Seattle, and another direct bus to Tacoma, with smaller busses going to other stops in between. I appreciated that, because it probably got me home maybe 45 minutes sooner, though still about 12 hours delayed.
Unfortunately, the Tacoma station staff was horrible when the bus dropped us off. We arrived before official opening time, and although a station agent was inside and working at the counter, she refused to open to the door, instead leaving several elderly folks to stand outside in the drizzle for 45 minutes until the station officially opened. They really could have / should have allowed the passengers from the bus to go inside to use the rest-room and sit without fully opening the station. But no, the agent just came to the inside of the door, pointed to the opening time, and then walked away. Terrible customer service there. Maybe she didn't know we were passengers arriving after a 12-hour delay and maybe deserving of some reception, but she should have. (I took a Lyft home, and offered to give rides to anyone who wanted a lift to a coffee shop or some other warm location.)
Summary: Unfortunate incident with one death. Some Amtrak employees shined, some were embarrassments.