You can’t predict whether you’ll become part of a queue at the next traffic light, or whether a bus will come up behind that queue.

You can't predict it perfectly, but you can often do a very good job. For example, say you're wanting to take the next right turn, and the lane becomes a combined bus lane + right turn lane not very far ahead of you. If you don't see a bus and you pull into the lane a bit early you have an extremely good chance of making it to the combined section before a bus comes. Similarly, the buses all have transponders on them broadcasting their locations, so you could be running a bus-aware navigation app on your phone.

In addition, a camera on a bus might only be able to see the license plate on the last car in the queue, when cars in front are equally culpable.

I think this is fine? Yes, you only enforce the rule against the car immediately in front of the bus, punishment for being at the end of a queue should be enough to keep queues from forming where they would be in the way: joining the queue is risky because maybe no one joins it after you and then a bus comes.

Before the bus lane, there was no delay for the bus.

I'm not sure where you're talking about, but as someone who commuted on buses for years (mostly the 94 into Davis, but a range of others as well) this was rarely my experience. Buses were regularly caught in traffic.

even if every bus were crush loaded, the bus lane could carry a fraction as many people as a lane full of single-occupant cars

A lane operating at ideal capacity allows about 1,900 cars per hour, but in the sort of very trafficy situations we're talking about we're well below that, maybe more like 600 (a car passing every 6s on average, but very uneven with periods of no movement). The cars are almost all one person each, so this is 600 people per hour.

A "crush loaded" bus would be about 75 people, so you'd need ~8 buses per hour, or one every 7.5min (or a lane that serves two lines running every 15min or four running every 30min). That's probably more frequent service than most of these lanes get, but I'm not sure? If it is, though, it's not by that much: a bus lane can still look "mostly unused" while carrying more traffic than a congested car lane.

The bus lanes around here are often marked really badly, with very few signs in a very small font, and pavement markings that aren’t maintained as they fade or the road is patched.

I haven't seen that (where I've driven the lanes are a very clear solid red) but if it's happening that just seems like a reason to mark it more clearly? Keeping the lane but not ticketing drivers who block the buses seems much worse?

And some of the bus lanes don’t even have any buses using them! The city and state striped a lot of bus lanes for the October 2022 Orange Line shuttle, but didn’t bother to remove them. Why should people get camera tickets when the people making the rules are this sloppy?

I agree if they're not in use they should be removed, but I think you're missing how my proposal helps with this. If you only enforce the bus lanes when drivers actually get in the way of a bus, then people who know that a line is marked for a bus route that is inactive are free to use the lane.

I'm proposing trying to bring the rules closer to what would have good consequences, which in this case combines with something that's easier to enforce.

Do you think this is evil in this case, especially if it is a completely reliable "get in the way of the bus, get a ticket"?