There's an argument either way...
COWs can be deployed very quickly, using microwave back-haul, so cell service can be restored in hours; albeit in a limited manner... (COW = Cell-site on wheels, either trailer or truck mounted cell sites, with collapsible towers, antenna segments, and microwave or satellite based uplinks).
Hardwired phones (ala pay-phones or hard-wired POTS to your house) are generally more resilient then over-the-air connections, so may survive incidents that knock out cell service; and are powered from the CO or remote, which will have batteries, and may or may not have a generator. As long as the CO has power, and the cable plant is intact, you'll have dialtone.
Cell's are 'easier' to knock out of service, but are also much quicker to restore; whereas an event that knocks out wired phones will require more labour-intensive recovery efforts.
With regards to salt water and OSP - salt-water is very corrosive to copper and other reactive metals... It can cause surface corrosion within hours. It's got to do with ionic activity more then ph - just because it won't eat your skin, doesn't mean it doesn't have very negative impacts on wiring.
Payphones are handy, no doubt - when you need one, you need one... But they are also expensive to maintain and operate, have a high rate of fraud and vandalism, and are generally money losers... I completely get why ILEC's want out of the business, or at least want to raise the rates to a break-even level.