I take the train around 450 times per year (one-way) and I've been doing that for around 11 years, so that's around 5000 train trips. Caltrain runs around 90 trains per day, or 450 during the week, about the same number I take in a year. Caltrain hits a pedestrian or vehicle around every 3 weeks, so at least one per month on weekday trains. I ride the train around 2/3 the total distance. That means I'd expect to be on a train which hits a pedestrian or car around once every six years. But I've never been on such a train, until now. I'm on the train now, logged in to a wireless network which happened to reach this position.
There's two bike cars per train. I usually get on the southernmost. That's what I did this evening. The northernmost is the lead car for the evening commute. The engine is to the south, pushing the train set ("consist" in train-speak). Cyclists in the northernmost car, the other bike car, reported the collision was loud and "scary". We heard and felt nothing. The lights went out, the train rolled to a smooth stop.
But I'm stuck here in the train for now. Now that the lights are back and I'm logged in it's not so bad: I have stuff to do. It's way better than being stuck on the highway with a vehicle crash. Bad days on the train are way better than bad days in a car.
Probabilities are strange. Ride the train more than a decade, and it's probable you'll be on a train which hits a car or person. So it's not surprising it happened to me. But it is surprising it happened at the moment it did, on the day it did. But it's perhaps not super-surprising it happened where it did. San Bruno is notorious for car-train collisions: this is the third in just a few months. The first was with a truck, the second with a car, and now this one with another truck. At least nobody has been hurt in any of the three incidents. Suicides have got to be way, way worse, mostly for the driver and conductors, but also for the passengers. So far, fingers crossed, I've not been on a train encountering a suicide.
appendix: We eventually got picked up by another train. I'd been sent an email it had been a truck we'd hit, but it was a car: empty. I got home around 8:30 pm. Not so bad: I spent time on the train catching up on emails once the lights came back on and I was able to guess the password of a nearby wireless network.