Where I am, there are probably a maximum of 20 lines on te cable from the cabinet. I was an early adopter and there was no forecast at that time - however when I received around 65Mbps, I was happy as it tied in with the line length, maybe a little slow but totally acceptable. Other estimates for properties on that cable were all slightly above mine - I am the last.
When I had an issue, the BT tech actually located a bad connection in an underground chamber that was totally "hidden". That pushed my speed up to around 74Mbps.
Within a few weeks all of the line estimates towards my end of the cable actually then increased.
So, proof that real data is fed back and estimates can go up as well as down.
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taurus excreta cerebrum vincit