Obviously this is about the power outage in Spain.
While normally, if a card declines, people would probably have to leave their IDs with the restaurant while they went to get a withdrawl from their bank; this is a power outage, withdrawls wouldn’t work. It would be silly to arrest people because of a power outage. So I’m assuming people just have to give the restaurant owner/management their identity info with a promise to pay?
And power outages shouldn’t affect buses, since they run on gasoline/diesel, but the payment system processing transit passes might not work. Do buses still get run during a power outage and they just let people on for free, or do they just shut down the bus lines?
Most cell towers have generators but only about 2-3 days of fuel. So you might have ways to charge your phone but it might not have a network to connect to
You don’t need a cell signal to get a GPS location so having some offline maps like OrganicMaps or OSMand can still be useful
Another point on this, in events like this the cell network is often under very significant stress as every single person tries to contact their family and friends at the same time to check if they are OK. The general advice is to avoid making phone calls if you can to keep capacity free for people who need to contact emergency services
Cell towers only have about half an hour of battery back up. Its the switched network (landline phones) that will last for a few days.
This depends on where and why. I know that in some parts of the Carribbean, for example, most towers will only last a day or two, but there are some that can last weeks with satellite backhauls providing minimal service to large areas.