Not sure it's a cable break
The cable cut idea doesn't sound very likely to me. This is an outage affecting access to their Ethernet services around Europe. Businesses in the UK have lost their ethernet IP access, as have those in Dublin, Brussels and Milan. Besides, the Colt network is peered with many other networks on both sides of the channel, so the whole thing shouldn't go down.
Apparently the hardware vendors have been called in to try diagnose the problem from traffic captures, which makes it sound like a multiple simultaneous hardware failure. Perhaps some kind of cascade failure or one of these "look how easily routing can be subverted" attacks that the doom-mongers have been predicting for years.
Whatever the reason, I don't envy the Colt engineers right now!