Not read full report yet,
but depends on what fibre you mean. If it means ability to unbundle the fibre to the home then issues may arise due to topology used. The Openreach setup lends itself to bitstream unbundling, but not actual unbundling of physical fibres.
It may be refering to backhaul too, or some combination of these in an attempt to make offering LLU and future services more attractive in Market 1 and 2 areas.
Thirdly there is the issue of sub loop unbundling, which is considered too expensive to do at present (apart from in South Yorkshire).
Ofcom isfollowing its mandate of competition is king, and reducing BT's cut is good, and many will agree with that view.