That’s not how traffic rules work, and for good reason. 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. 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 the camera bill is a bad idea for several reasons.
The bus lane implementations around here were done really badly. Many of them created traffic jams that didn’t use to exist. Before the bus lane, there was no delay for the bus.
In addition, the scheduled service in many of these lanes is so sparse that 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 real bus lane like the one approaching the Lincoln Tunnel in New Jersey serves more than a hundred thousand people every morning.
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.
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 that this is a risk, and it's possible that it's enough that this is a bad idea. I'm especially worried about very long stretches where you can see that a car is coming along, and so have plenty of time to pull out in front of it.
But I see two main mitigations:
Cutting other drivers off would still be a traffic violation and people don't want to cause accidents, so I don't think we get the worst behavior of sudden lane switching.
People might only use these lanes close enough to when they know that they are going to be getting out of them that they won't people vulnerable to other people getting in front of them.
I think bus lanes are great: the faster you make buses the more people switch from cars, which means the more frequently you can run the buses, which means even more people switch from cars. But when there's traffic drivers are often tempted to sneak over. The chances of getting a ticket are pretty low, other people are doing it, and then when a bus does come through there are cars in its way. Which loses much of the benefit of setting aside a lane for buses.
Some places (ex: NYC) handle this by putting automated traffic enforcement cameras on buses, and this was proposed for MA with Bill H.2494. [1] I think this is a good idea, but I'd like to see this go even further: put cameras on all the buses and then don't enforce it otherwise.
The idea is, in cases where you don't delay a bus then by using the lane you're making traffic a bit better for everyone else. You might be about to make a right turn, you can see that there's no bus coming, and you're going to be out of the way before any bus you don't see yet would be near. Or you're using a GPS for navigation which also knows the real-time bus locations, and it tells you you're safe to use the lane. By limiting enforcement to only cases when someone actually does delay a bus, it ought to be possible to both keep the lane clear for buses with less waste.
Since some people would still be scrupulous and want to stay out of the "buses only" lane regardless, I'd also want to see us change the law from "no cars" to "no cars slowing down the bus".
[1] The bill history ends with "1/3/2023, House: No further action taken". I'm not sure exactly but I think maybe because it was a bill in the 192nd congress and we're now on the 193rd this means it's dead?