It wasn't possible to prove that the investigation was reopened because new evidence appeared. Possibly because the details weren't released. The matter of new evidence was raised again by the McCann's lawyers in the request for an annulment of the SC judgement.
However, inside the factual matter established as proved in the minutes, there is no fact capable of constituting ground for the review or reopening of the investigation in question,
http://www.gerrymccannsblogs.co.uk/Annulment_request.htm
They seem to be saying that there was nothing to justify the review or the reopening within the existing evidence. The PJ review began, unannounced, in March 2011; before Operation Grange began.
With that objective, the National Director of the Judiciary Police, in March 2011, assigned to a team of investigators from the North Directorate a task to re-examine the whole wide range of information contained in the inquest, with the aim to identify information whose further understanding could be revealed useful and possible.
That reanalysis task, which took place during the last two and a half years, helped identify new evidence, which by imposing further investigation, meet the requirements set by article 279º no 1 of the Code of Criminal Procedure for the reopening of the investigation.
http://www.gerrymccannsblogs.co.uk/Nigel/id466.htm
That sounds like the review wasn't preceded by the discovery of new evidence to me, it sounds like a fishing expedition to me. Cases archived under 277/1 could only be reviewed or reopened if brand new evidence appeared which was not in the investigator's possession at the time of archiving.
Would potentially relevant information that had previously been inadequately examined and simply filed constitute "new" or not?
Were the assaults on children ever investigated? If so, I can find nothing to indicate any resolution of those cases. And if so, was any potential connection between those cases and Madeleine's disappearance investigated at the time?
Information on discrete crimes could be held (therefore not technically "new") in various files, possibly by different forces, but simply a lack of resources (in the broadest sense) might not have brought to light a potentially credible, but unexplored potential connection.
If that potential connection had then been spotted, would that be a "new" element warranting serious investigation, or would it not be new as the background information had already been received but was lying in a dusty file somewhere?
