There have been some reports of leads on the number but nothing definitive. I'm not sure whether LE would openly tell us if they did know the caller by now though if they are still gathering other evidence.
I recall there was a supposedly promising lead from the XY program in Germany but never heard anything about it afterwards. What I have found a little odd is that in all the subsequent TV appearances by HCW, I have not seen him reiterate their appeal for information on the phone numbers. Maybe they already know, maybe they don't.
Maddie cops probe new 'phone link' to prime suspect Christian B after TV tip-off
"A viewer of Germany’s Crimewatch called cops to say they recognised a mobile number that suspect Christian B is said to have phoned on the night Madeleine vanished.
Police now hope to trace the Portuguese number’s owner. They are also checking banks in Portugal to see if it was topped up at an ATM.
In the new TV appeal about three-year-old Madeleine’s 2007 disappearance, German police urged viewers to check diaries and contacts books to see if they recognised the number.
As the show ended, detective Alfred Hettmer revealed: “There have been 16 calls about this number and one of them is promising.”
The caller had contacted police in Bavaria — significant because that is where convicted paedo B lived before moving to Portugal"