Thomas Horne wrote:

Tony Hwang wrote:
....
Tony
Wires don't break just because the utility power goes out but cell site
batteries don't last for ever without it. Point is that you don't
depend on just one means of communication. An exchange powered copper
pair line is an excellent means to keep a pathway open when the a power
outage is the problem.
--
Tom Horne
Some copper pair land lines depend upon power that does not come
from the central office. About a month ago, after less about a
day of power failure, the phone went out (but DSL kept working
for a while!!). It turns out that there is fiber optic from the
central office to an equipment shack in the field. Power comes
from the utility, then back up batteries, then a back up generator,
but someone has to go out into the field to start the generator.

What really matters for reliability is not the technology
(land line vs. cell), but the reliability expectations, and what
the service providers will do to meet those expectations.
Currently, we expect land lines to be there all the time and
get very upset if there is one outage a year. We expect cell
sites and entire network regions to go down frequently.
Consequently, land lines have back up batteries and generators
(usually automatic!), and cell sites might have a battery.