SY haven't taken over the investigation at all. They started a new one because they were instructed to by the Prime Minister - no other reason.
Operation Grange was set up in 2011 to review Madeleine McCann's case.
http://content.met.police.uk/Article/Operation-Grange/1400005508791/35434There was sufficient evidence in 2013 - after reviewing the files for two years - to allow the recommendation to be forwarded that Madeleine's case should be reopened.
No new inquiry ... just a fresh unbiased look at cold case evidence which wasn't properly worked at the time ... and the reopening of her case ... proving the evidence was there for seven years.
So the apologists for that incompetence, cannot pin the failure of Madeleine's case on her mum's refusal to answer 48 self incriminating questions ... the blame for that can and should be laid directly at the feet of incompetent police work.
Yard has 'the best opportunity' to find Madeleine McCann
A 'cold case' review of the Madeleine McCann case has led Scotland Yard detectives to identify potential suspects involved in her disappearance from an Algarve resort
By Padraic Flanagan
11:37AM GMT 19 Mar 2014
Operation Grange, staffed by a team of Scotland Yard's finest detectives and paid for by the Home Office, offers the best opportunity to find out what happened to Madeleine McCann.
While the Yard cannot rectify the mistakes made in the initial inquiry, when the Portuguese police were accused of failing to seal off the area where Madeleine had been staying and gather all available forensic evidence,
the inquiry team has had access to all the files.
This has enabled detectives to look at the case with an
objective eye and form fresh theories about what may have happened to Madeleine. Their determination has prompted quiet optimism that a breakthrough may be possible.
The review has led detectives to uncover
“new evidence and new witnesses” in the case. Among the most recent revelations was the Yard’s desire to interview three burglars who were in Praia da Luz when Madeleine went missing.
It has also emerged that the Met Police have identified more than 40 “persons of interest”
after reviewing all the evidence, and have formally asked Portugal for more help with their inquiry, which has been running since 2011.
http://www.telegraph.co.uk/news/newstopics/madeleinemccann/10707520/Yard-has-the-best-opportunity-to-find-Madeleine-McCann.html