The alternative way of laying fibre involves digging up the road which can be extremely disruptive, expensive and slow
This is a load of rubbish. BT will have plenty of spare duct space for fibre networks, There's a four inch duct running down our lane that has one
50 pair CU cable in it that can't be an inch in diameter.
There were at least two 97 fibre mega-stream 'ring mains' round the city in 1993 so will be several more now. The real problem is that 'domestic' fibre installation just isn't worth the investment, and another is the BT own most of the duct space.