In their slides, the first bits are an unique id (it's also printed on my MTA card (from NYC) under the date). This doesn't make you personally identifiable if

In their slides, the first bits are an unique id (it's also printed on my MTA card (from NYC) under the date). This doesn't make you personally identifiable if you paid cash for the card, but it's an unique to the card, so discrepancies could be caught pretty easily.