With the new version of Content translation, now there are several mechanisms that can help with this. This should be enough for most of the purposes (review problematic translations, inspecting a particular translation and getting a general overview), so I'm closing the ticket (feel free to reopen if that's not the case), and detailing each case below:

Review problematic translations: tracking categories.

For each language you can find a tracking category where the translations that were published and may have not been reviewed enough are included. You can check the documentation here. This allows to focus the review on those translation that while complying with the limits to be allowed to publish, for some paragraphs the initial machine translation was not edited enough for some paragraphs.

• Inspecting a particular translation: Translation debugger.**

The translation debugger allows to capture information about a specific translation. you can add the codes for the source and target languages and the source article title to get the metadata about the translation. This includes the "progress" field:

progress {"any":0.9583333333333334,"human":0.7083333333333334,"mt":0.25,"mtSectionsCount":6,"translatedSectionsCount":23}

In this example, the overall translation contains 25% of machine translation ("mt"), for example.

If you click on "Fetch translation", you can get information on the translation service used for each paragraph (note that users may use MT for a paragraph and not use it for another).

Getting a general overview: APIs and stats
As mentioned earlier, using our data APIs and dumps about published translations allows to capture the information to use it in other ways. This graph provides an overview of the number of articles in which each translation service is used (including those cases where no MT is used).