Great Western Coffee Shop

You may have seen reports of this incident in some British media, and here is one from The Local (https://www.thelocal.fr/20180801/power-cut-leaves-hundreds-stranded-in-sweltering-paris-metro-trains)

As you can see from the picture, this is line has rubber-tyred trains and a 750V DC third rail supply. It is also automatic, being one of the older lines where this has been introduced. Those both had implications, which come through in RATP's published account (https://www.ratp.fr/groupe-ratp/newsroom/metro/retour-sur-lincident-du-mardi-31-juillet-sur-la-ligne-1-du-metro).

The line runs east-west from Gare de Lyon to La Defense, paralleling RER A which is currently shut for track replacement. Thus trains were running flat out on L1, every 90 seconds. When one train failed, those behind were stopped where they were with little room for movement, and twelve were in tunnel. So the procedure mow is for someone to walk to the failed train to try to sort it or move it manually. that means turning off the power there, and of course it adds a delay before whatever would happen with a driver present.

After 30 minutes waiting, people started operating the emergency alarms, which led to the power being turned off so the trains lost full lighting and all ventilation. Presumably anyone forcing doors open would also be sensed and turn off the track power. Phone and help point calls swamped the call centre, unsurprisingly, though RATP claims they kept using twitter and on-board screen and voice information (though don't tell us what was said).

Evacuation is (as with the Underground) from the train's ends via a ladder, though there is just enough space to get out of the sides, less easily. That took until 22:30, 2.5 hours from the incident start. RATP are currently saying they did as well as should be expected for such an "exceptional" incident. No doubt the minister will call for a report, in any case.

Guess what? It's happened again! This time it was line 14 that suffered a power cut, but that is the other, original, driverless line having been built that way from the start (1998).

The details, from RATP, are that power was lost from the whole line from 19:00 to 22:30 yesterday (29th). Nine trains were involved, some at least partially platformed. Staff (100 of them) went out to lead passengers out on foot, taking up to an hour to reach them, and everyone was out by 22:00 (some reports say an hour earlier).

At least it wasn't as hot as last time. Plus, having had a top-quality (almost like the real thing!) rehearsal only a month ago, RATP do seem to have done a lot better at giving the right information and getting enough helpers. There were still complaints that the walking route was dark and uneven, with holes that could trip you. And all those late for a Britney Spears concert at Bercy were a bit unhappy too.

Thats interesting.  The whole purpose of emergency tunnel lighting is that, err, its available during a power cut..... ::) :P

I understand there was lighting - it just wasn't good enough to prevent at least one passenger getting her foot caught in a hole and hurting her leg.

In practice it seems to be provided in case the train beaks down, or in the specific case that the traction current fails, rather than for any more generalised power failure.
In the case of LUL tunnels, the lights are supplied from the national grid, not from a generator, battery bank, or other emergency supply.