They may have policies, but most aren't like you think. Police and other emergency personnel take meal and other breaks out in the field. Because it's preferred that are available if/when called, they need to stay close to their cars. Parking in NYC is scarce, so it's not like there are empty spaces all over. Given a choice between losing time looking and ending up parking 2 blocks from a donut shop, they do the best they can under the circumstances. This might mean double parking, or blocking a bike lane or fire hydrant, or even across a driveway.

These are the realities of life in NYC, where situational adjustment trumps theoretical "policy".