Ofcom were hoodwinked.
It was all just vapourware announcements by Virgin Media to prevent the full separation of Openreach at the time, "Look Ofcom competition is really working, we have big plans". Neither VM or BT wanted full Openreach separation (and it's still a distant Ofcom threat, remember, that part hasn't changed, if there isn't even greater degree of infrastructure spending by BT).
Ultimately, the roose/flattery towards Ofcom (to show Ofcom's role was a worthy one) worked at the time, but doubt Ofcom are too pleased being hoodwinked like this.
Ofcom (and Ofgem) regulators really need to stop being such Narcistical Organisations, looking for self praise/damage limitation against the regulator themselves, when there is vocal criticism of the regulator and its role, because its a factor telcom companies like BT will use to their own advantage against the regulator. It's a visible weakness of UK regulation, its own "narcissism", there to exploit.