Hi, I worked EMS in NYC, hospital based, BLS from 3/03 to 10/05, and ALS from 10/05 to 10/07.
Units are broken up into either BLS or ALS. The unit's number identifies it's home batallion, and the letter denotes ALS or BLS. A,B,C,D and so on are BLS. S,U,V,Y,etc. designate ALS. Henry and Zebra units are Haz-Tac, units that are hazmat trained. So, 46Young is an ALS unit in the 46 batallion.
Most units have a designated street corner from which they respond, called a CSL, or "89". BLS units are dispatched to lower priority calls (jobs), along with cardiac arrests, and any ALS call where the medic unit has an ETA of more than 10 minutes. ALS units are only dispatched to high priority call types, not for sick calls, injuries, EDP's, conscious ETOH, etc.
BLS units can be any combination of EMT and medic, but have only BLS equipment, and are restricted to BLS protocols. ALS units must be double medic. Here are the protocols:
http://www.nycremsco.org/
When enroute to the hospital, the crew will only give notification to the hospital with a seriously ill pt. The driver will give a brief notification to the dispatcher, who then calls the ED. I like this method as it frees up the medics to work on the pt without the ED staff hassling them with more questions when work needs to get done.
NYC 911 EMS is controlled by the FDNY, who dictates GOP's, SOP's, protocols, and employs single role medics. Suppression units are CFR-D certified only, and dispatch to high priority ALS calls only. Hospital based and private EMS providers also operate within the system, under a FDNY contract.
The general rule of thought is that if you want the benefits, go with FDNY. If you want better pay, better schedules and working conditions, and want to go to college to progress to another career, go with the hospitals. If you can't ge thired otherwise, if you're waiting on FDNY or a hospital, then go private.
When I left in "07, the city averaged around 3000-3500 calls/day citywide.
EMS works 8 hour days, although I've heard that they're experimenting with 12's.
What else do you want to know?