It depends a lot on what time you take the train IME. At 8am it's nearly 100%, on a Friday evening it's closer to 20%.
And of course on the rare occasion a staff member challenges someone not wearing a mask, they claim they're exempt and don't have to provide any proof.
And of course on the rare occasion a staff member challenges someone not wearing a mask, they claim they're exempt and don't have to provide any proof.