... so I might as well tell you too. Info gathered by joggling the elbows of the people on #wikimedia-tech actually doing the work:
This was two overland cables between Tampa and Virginia (Washington DC, to be precise). *Both* cables were cut, near the Tampa end. The "redundant" fibre wasn't redundant. Currently awaiting the vendor postmortem.
The cables were broken for 1 hour 6 minutes, but it's taken another hour to bring up basic service. Some stuff's still broken. Search and API (hence mobile) are back now. It'll all be back in due course.
The WMF office in San Francisco should be getting into work in the next hour or so ... should have more detail then.
- d.