2. The iPhone can detect the distance to the AirTag quite precisely. I think this type of false positive is going to be rare enough for notification fatigue not being a problem. In your bus example, reporting the false positive would be fine imo. (It would also allow you to return the air tag to the owner).
3. The notifications don't go through Apple's servers, so Apple would need a backdoor in the OS to disable the feature. They might have added something like this, but it might not matter much - if someone plants a tracking device on you, they'll use one without silly privacy features.
AirTags are BLE beacons, that Android phones will simply not pick up and not send their signal to the mothership. A background noise.
If an Android user is travelling with an AirTag other people (e.g. a colleague) with iPhones will "send the signal to the motherships" but they won't get the alert as they most likely won't be in proximity of the AirTag long enough to trigger it.
A few days ago I was trying to figure out what an AirTag is, so I read the Apple website. They claim that ordinary people don't need to worry about being tracked, because users who are travelling with an AirTag that is not theirs will have an alert sent their iPhone.
This raises three questions which were conveniently elided on Apple's website:
1. What prevents people from using AirTags to track Android users?
2. How does the notification balance false positives, true positives, and notification fatigue in the situations where "someone next to me on the bus leaves an AirTag behind." How is it distinguishable from "someone snuck one into my pocket on the bus"?
3. Under what circumstances will Apple be willing to suppress the notification that one is being tracked by an AirTag?