Fairly obviously, the SOTAP kit continues to provide power from the local exchange so even in the (relatively common) power cuts here the phones continue to work (we're not on any kind of priority register or anything like that, I assume it's just BT are dealing with peopole living out in the sticks).
N.B. we also have a 2nd line, on a business account (WFH) - that one is full digital, 70mbps VDSL and has cisco/yealink ATAs for phone service. So two lines, a home line that's SOTAP and a work line that's broadband/digital voice.
[1] https://www.ispreview.co.uk/index.php/2025/09/openreach-laun...