Tour de France 2015

They got the data from Training Peaks allegedly, not from Sky. Could have been obtained in numerous ways:

• Hack TP to have access to all data for anyone (unlikely)
  
• Target an TP account that has access to Froome's data either by 'hacking' or social engineering someone who has that access (maybe)
  
• Find it because someone accidentally left it, a link to it, or login credentials lying around (e.g. unscrubbed laptop) or a URL visible in a PowerPoint presentation (possibly)
  
• Get it from someone who works at TP itself (most likely)