Some years ago, terrorists attacked the London public transport system.
As a consequence there was no effective cellphone service over most of London.
Power was out in places, but only very close to the explosions, there was no general or widespread outage. (I suspect either blast damage to utility equipment, or local flooding from water pipes broken by the blast)
This put my then employers to substantial inconvienience as their business was spread over a number of buildings and heavily reliant on messengers with cellphones.
Many staff were distressed at not being able to contact friends , workmates or relatives.
It was most fortunate that I had about a mile of telephone cable by means of which land line phones could be used externally, simply throw the cable out of the window.
This was mainly for use of staff, but several police officers asked to use the phone, as the police radio system was overloaded.
Walkie talkies worked fine, but we only had 6, and only had means of charging them at one building.
When the immediate emergency was over, I extended my phone line into the local pub, in order to stay in touch as there was still no cellphone service.

an old touch tone phone, short section of cable to hook into a "borrowed" external phone box + an adapter for the cable to a couple of alligator clips for temp hookup

I get reliable 3mile service (typically more) out of a peaked CB with a good magnetic mount antenna (1:1 SWR) on SUV... receives NOAA WX 60mile to Ruskin, Fla

Reliability is great. But it's more understandable if you specify more about the system.

Reliable over what distance? In what conditions? Connecting with who? For what purpose?

There are lots of answers to the original question in this thread but each of the answers assumes different scenarios. So they only make sense if you know what scenario is being assumed.

I'm a Reliability Eengineer by job title and a radio geek since vacuum tubes. But I don't have enough info to give my answer to the question. I'm surprised at how many have.

Well, the quality of the info you'd pick up couldn't be any worse than what passes for journalism these days.

Part of the skill of being a ham is knowing how to pass traffic in a controlled net.

Net Control, this is shelter 2 with priority Traffic, - kg2v

Silly man. Vacuums have bags or cannisters, not tubes.

For the passing of simple pre arranged messages, rather than 2 way voice contact, dont forget such basics as colored flags or similar by day, and colored lamps at night.
In clear weather ranges of some miles are easily achieved.

This can be a usefull suplement to cellphones, walkie talkies, or ham radio if battery power is very short.
A simple pre-arranged code could save scarce battery power.

RED-------------turn on radio or phone ASAP and make contact
YELLOW----------radio/phone defective.
GREEN-----------All is well, no need to consume battery power.
BLUE------------Make contact briefly at 18-00 local time.

Or some other system as required by local conditions.

A coloured lamp need not be electric, oil lamps for railway purposes are still available and give a red, green or white light.
A single 5mm LED consumes less than 0.1 watt and can be seen for miles if correctly aligned.
A flag of course requires no power or fuel.

You of course realize that most RF AMps still use tubes, often ridiculously expensive tubes - Luckly my amp (used) had brand new tubes in it when I bought it - a matched set of 3 tubes would run me close to $1300

No, I didn't actually.

My uncle and aunt are on again/off again HAM's. I never caught the bug.

When your house loss power, land line phone and mobile handset not operational. Your shouts for help is not heard by your nearest neighbour. In such a situation, a walkie talkie would be very helpful to get your message across to your neighbour.

But for walkie talkie to work in time of disaster. Some preparations is necessary.
Pre-disaster
- distribute walkie talkie units to your immediate neighbour

During disaster
- monitor the network for any request for assistance
- set a specific time to do touch base daily during disaster

Post-disaster
- assist with recovery process

Advantages of walkie talkie
- free
- limited range (enough range to reach your neighbour)

I did not mentioned CB because it can easily communicate with another party 50miles. But may have problem reaching your intended neighbour that is 1 or 2 miles away from you.