how does all this work with rental cars?

Presumably the same as it does with speeding citations. You get a bill
from the rental car company after the fact along with a hefty administrative
surcharge.

It's the "hefty administrative surcharge" I was concerned about.

In my actualy experience, the surcharge is $2 or $3. You can decide whether that
counts as hefty, in the context of everything else you pay for a car rental.

Considering that people often pay $10/day for the rental company's overpriced
insurance, it doesn't seem very hefty to me.

R's,
John