The only time I’ve seen them mentioned is in news reports about their existence as a campaign, never actual usage.
Another interesting campaign around corruption is ipaidabribe.com to gain some data around this. Unfortunately, both giving and taking bribes is illegal, thus you need anonymity for reports resulting in a lower data quality.
To fix that, there’s proposals to make it legal to pay “harassment bribes” (the ones where the bribe giver does not gain undue advantage).
> Giving complete immunity to the bribe-giver would ensure higher reporting and co-operation of the giver in bringing to justice the bribe taker. The present law acts as a deterrent to reporting of bribery.
https://prsindia.org/theprsblog/should-bribe-giving-be-legal...