As others have asked here I should be astonished that a massive outage can be caused by a single broken fibre cable. It should be punishable that they have a single source of failure that can affect all of their T-Mobile customers nationwide. As others have also said it can only be due to cost cutting that this has happened. That or gross negligence!
The thing that has annoyed me more than anything though is that I had to hunt down a WiFi signal while out then search for reports of problems just to discover that there was a problem. The main suspect until that point was my phone because I had full signal and 3G / H+ signal showing the whole time. For a massive communication company with so many customers they don't appear to know how to communicate with customers unless it's to demand money or to try and sell them new services.
Last things to mention. Until this post on El Reg I have seen no reports of this anywhere else except the Daily Fail of all places. The forum posts from EE were mentioning hourly updates which, naturally, didn't happen and of course there was no sign of a real apology or explanation for how they could screw up so badly. I don't know who will bother beyond me but I'm on a 30 day SIM only deal so this is the final nail in the coffin so to speak. I have no loyalty to a company that I've been with for the best part of 5 years who couldn't even match a SIM only price with 3 or offer the same allowances.