I understand subways and traffic lights stopped during the blackout, and some areas lost water as well. How about other utilities and services such as gas, telephone, cell phone and Internet providers (assuming you have a working phone and a battery powered laptop)?
Cell service was badly affected - sites either lost power and were disabled, and functional sites were quickly overloaded.
ISPs would hopefully have their equipment connected to a UPS system to provide at least a few minutes operation on batteries, then execute a safe and orderly shutdown.
Data centers at banks, the stock exchange, etc. run their servers on UPS, and after a few minutes, the diesel generators kick in. (At this building, this happens after five minutes) If it looks to be a sustained outage, a tanker of diesel fuel is dispatched.
The telephone system runs on batteries to begin with, so they don’t need a UPS system. After however minutes without power, backup generators kick in and someone is called to deliver a tanker of diesel fuel.