The key difference with Optimum / Cablevision / Altice Fiber (and Coax) infrastructure is that unlike FiOS, Cablevision {etc) relies on Utility power. If you experience a power outage in your area, service will go out. FiOS is powered from the headend so provided there is no break in the physical fiber cable, service works during a utility power outage provided that you have a generator or battery backup to power the ONT (Fiber Unit) and Router / TV / Phone.
Optimum does have battery equipment at certain points in the network, to the point where they rented cable modems with VoIP (f/k/a Optimum Voice, now Optimum Phone) that had slots with battery power that you could purchase. The battery (if purchased) a subscriber could put in their modem would provide eight hours of service on the eMTA interface of the modem (essentially, you could still make calls). That does have upstream power requirements as well, and the Cablevision/Optimum of many years ago was good at maintaining the batteries on the street. Not so much these days, although sometimes public utility commission complaints can get their ass in gear if you have an example where you had power (generator/battery) but service didn't operate.
FiOS indeed only needs power at the headend; at least the earlier ONTs they installed, those had sealed lead acid batteries (typical of cars, or in smaller formats, for alarm systems and uninterruptible power supplies for key equipment) in them. Of course, SLAs have a lifetime (generally about 4-5 years), and many people don't even know they're in there, or how to replace them (
not hard). This can be a more economical solution to at least keep your phone active for emergencies if you have voice service on FiOS (or if you're not up for a whole home generator, in tandem with a UPS for your modem/router on FiOS, to at least have internet service during a power outage.)
(Also, comments on YouTube seem to indicate that Verizon replaces the SLAs in ONTs for free if you call/chat them that the alarm/light for it is going off on your ONT. In terms of disposal, at least in New York, any shop selling lead acid batteries has to take at least two of them for recycling free of charge, even if you didn't buy any new batteries from that store... I usually get the replacement batteries for my UPS on Amazon, and then recycle the old ones at Advance Auto Parts.)