It's not "how much data could my network handle at peak" but rather "what is the maximum amount of information I can send through a network" where this 'maximum' is usually only attainable in ideal conditions.
The summary is somewhat misleading since "capacity" relates to "information", in the information theory sense and "data" relates to the idea most posters seem to have (i.e. the kbps you download at).
Also the arxiv.org paper is two years old but the work in Network Coding is very interesting and has been a very rapidly increasing field in the past years. I'm not from Caltech or M.I.T. but Medard is awesome and so is his work, just saying.