They have been discussing it here in Italy as well.
The isp/telecommunication industry here is tryng to get Cos/pops/cabinets listed as critical infra and removed from rolling power cuts.
I would say plan for the worst, because there will always be some other department or governmental function that says they are more critical than the next one. And even if they may designate certain functions as critical, electrical distribution grids are not always built to that degree of granularity, and those critical functions are often caught in the crossfire as other non-critical loads are shed from the network.
And even after all that, if the blackouts need to intensify, all bets are off, since the main purpose then becomes preventing grid frequency drop, rather than servicing loads.
Here this is mainly ran from pops that have ups and generator systems so several hours to days of uptime depending on site.
If major data centres need to spend more on fuel than they planned for, I'd suggest making a generous allocation for an increase in co-lo costs for your next budget cycle, as the data centres will, invariably, pass those costs on the longer the city has to shed power from the grid.
OTOH I have seen providers daisy chain customer sites in a ring that crash miserably when 2 customers loose power isolating all in between sites.
But that is not the norm...
This is one of the reasons we refuse to turn customer sites into Metro-E PoP's, or PoP's of any kind.
Street cabinets for fttc services here have low times if any.
Same thing for mini dslams mounted on poles in the middle of nowhere.
0 to 2 hours for these.
Most have batteries/capacitors in the cabinet but not all and they are not designed for extended power outages 2 hours max.
Some are remotely powered from the CO, but that does not seem to be a thing anymore. Too costly
DSL ran from COs are protected as for fiber above.
A lot of this will be driven by what competitors do. If there is no competition that can keep their street cabinets going, the others won't. It's a great opportunity for anyone willing to make lemonade out of the situation.
Don't operate a 4g network, so take this info accordingly , but here it depends on the tower from what I have seen.
All towers I have seen have battery backup , a lot have generators too.
I would say they have higher times than the fttc times above.
In dense metro's, mobile sites will be well invested. It starts to get tricky when you go out into the sticks.
Also, when the power goes out, so does the wi-fi. That means everybody moves their traffic away from the home wi-fi and on to the nearest cell tower. While radio bandwidth and signal coverage does not suffer that much, it hits the backhaul hard, between the tower and the mobile carrier's core. So nice flashing LTE/4G/5G signals on your phone translates to GPRS-esque performance. In some cases, we have seen mobile operators downgrade radio coverage to 3G, in order to manage this. Who knew 3G performed a bad as GPRS or EDGE, in 2023 :-)?
In the most extreme of case, the cell site could run out of power as well, as there isn't enough time for the batteries to recharge between outage cycles, or the field teams can't replenish fuel for the generators in time.
In the absolutely extreme cases (as we see here in South Africa, for example), cell sites can be raided and batteries stolen, especially if there is darkness all around. I would not expect this to be the case in the UK, especially if power outages are not the norm and people live a fairly middle-class life, but if I were Vodafone, for example, I'd have my risk department planning for such an eventuality already.