Comment Re:VOIP sucks. (Score 2, Informative) 426
For VOIP, they make these things called UPSes. A standard "10 minute" computer UPS can keep a cable (or DSL) modem, home router, and VOIP appliance running for hours.
Point being is there are no regulations that mandate cable providers (as ISP's or not) provide any level of protection against power outages. On the other hand, land-line providers are required to maintain battery AND generator backup. Cell towers are also exempt. Most have battery systems that will last for up to 60 minutes (most will not last that long due to battery age) and almost none have permanent generators.
Your only safe bet is POTS in a large scale power outage.