"Lets hope the current management has at least one working braincell unlike those back in the 90s"
'Fraid not. Two reasons for that:
1) All corporates who believe that M&A are a road to riches and success are misguided - transaction costs are high, there's a distraction from running the core business, you invariably end up with asset writedowns and goodwill to pay off, and integrating two large businesses effectively is a skill rarer than hen's teeth. Admittedly BT get access to the mobile market when this goes through, but they could have got that through a virtual MNO deal (buying some OFGEM firepower if the MNO's balked at agreeing a MVNO deal).
2) Companies have strong and enduring cultures that persist across generations of management. Look at how BT still have an arrogant, state monopolist mindset. Or how energy or water companies still offer standards of service biased towards the dismal standards of the public sector that they supposedly left twenty five years ago. Similarly BA's poor industrial relations. Even in the purely private sector corporate cultures persist for decades - for example John Lewis customer service, or (before they deservedly went bust) Comet's decades long attitude of "stuff your consumer rights, you're not getting your money back", or Ford's iffy reliability accompanied by an excellent parts organisation.
So I think we'll see the same old story. BT have a tame regulator who won't hold them to account, so that's on their side. They're buying from a moderately distressed seller. And they have vast market clout, and a big bag of cash. They've previously agreed FTTC as the limit of their fixed line broadband obligation, and suddenly it all becomes clear why they liked FTTC. Hook up the cabinet as backhaul connected to a multitude of small aerials fitted to the adjacent street furniture, and they're laughing - those cabinets suddenly become hugely valuable commercial assets, despite being paid out of the Openreach "regulatory" settlement, and not needing planning permission. Suddenly LLU grinds to a halt because "there's no spare capacity at the exchange", so that'll be competitors and business customers f***ed.
BT's customer-hating and inept management will be undoubtedly be able to snatch some small defeat from the jaws of this huge victory, but overall our former national telecoms monopolist will have just reconstructed itself, with (at best) a single second tier competitor in the shape of (perhaps) Vodafone/Virginmedia. As a big picture strategic play, BT's management have played a blinder here and I tip my hat to them if they pull it off, unfortunately this strategic success is very one sided and the only beneficiaries will be BT management and shareholders, with the losers including all mobile and fixed line customers and all competitors.