I'd say most on here already knew that (that there is an upper limit on the costs covered).
As always - the devil is in the detail.
Including how and when the "Incremental USO" (10Mbps is not fixed in the legislation, it's assumed to increase) will be re-evaluated, i.e. Yearly. You need a totally different design if BT errs cautiously and designs/implements for the next USO instead - 30Mbps, but guarantees 10Mbps, 2020.
The "Incremental USO" is the crucial point, that very much determines how Openreach implements the USO, in terms of patching its copper, to just meet threshold targets (upgrading 0.5mm to 0.65/0.9mm copper etc) or biting the bullet, stating all lines requesting this over 500m will be full, pure FTTP via reinforced fibre cables via telegraph poles. Initially it will be a bit of both, but it would be better to have said, that each proposal should err towards full/pure FTTP, so the solution being paid for by the consumer is a long term one.
Reinforced fibre cables via telegraph poles to eye-level green splitter boxes is the method being used in places like Ceredigion, West Wales as part of the Superfast Cymru Project. The only real problem with this method has been the time taken to avoid overhead power lines, due to the conductive metal reinforcement used in the cable, where high voltage Power/BT lines cross under each other.
In fairness to the contractors, once the topology design has been done, much of the fibre is put in place very quickly, often so quick in fact, most have trouble telling you when it actually happened.
Taking the pure fibre to a green fibre splitter box on the telegraph pole is a pretty good solution/half way house rurally, because BT then only have to do the ground works from there, for those that order, so if consumers were made to pay for the final works to the property, it's similar in cost for BT, to Pointless obfuscated, bamboozled "up to" copper carcass G.fast (in terms of the fibre install cost) with far more benefits for everyone involved.
The green pure fibre splitter boxes at eye level are a good solution rurally, a few though, are in locations where they will get ripped off by tractors turning, it has to be said. 'London folk' (designing this topology) don't always understand the biggest thing (farm machinery) down a country lane, might not care whether it catches a few hedges along it's route, where these splitter boxes sit.
In terms of pure fibre FTTP in cities; eye level green fibre splitter boxes in Birmingham? How long would those last?.