This is fixable. the corrupted data values are consistent amongst blocks in the same vein, such as the variants of snow, which currently have a data value of 1102, All the corrupted data values can be fixed if we can line them up with the correct data values.
MC-59581
14w26b Data corruption is reparable
Resolved
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0
Already done by a guy on Reddit: http://np.reddit.com/r/Minecraft/comments/29551r/if_you_corrupted_a_large_project_or_lost_a_large/cihnyjq