Does that assume that every cabinet on those exchanges is enabled?
Otherwise the real %-age population coverage is likely to be somewhat lower.
Yes - That "assumption" of using just the market 2 and 3 exchanges to make 88% would require every cabinet to be converted *and* that everyone on those cabinets would be within the (approx) 1500-2000 metre range to get the numbers to add up.
But the BDUK target is 90%, so if we assume that not everyone on a market 2/3 cabinet is capable of being covered, then *some* market 1 coverage must be happening too.
My personal assumption, though, is that getting to the 90% coverage is going to require some additional technology tactics on top of the existing one. I'm expecting BT to need to deploy smaller FTTC cabinets, further out in the network. This would be needed for people with small cabinets covering few premises. It may also be needed further out in the network than the existing cabinets, so as to reduce the D-side length.
Even with this, we need a solution for those with exchange-direct lines too.
If BT are going to continue with the existing size of FTTC cabinets, existing limitations (only putting FTTC cabinets where there are existing PCPs, and only allowing VDSL2 from a cabinet), then a lot of market 1 exchanges will need doing too.
That's one reason to look at the technology that will be chosen for Surrey. As this county is going for near-on 100% SFBB, it'll be interesting to see what adaptations are made to the existing tactics.