Operation Grange had 600 suspects at one time, they also had the phone data, but it took until 2017 when a bestest mate said CB did it, actually was that true or did he say CB told him he knew what happened, any how no one picked up on CB including the BKA in 2013 when they talked to CB.
The reports I've seen are that Busching claimed Brueckner would 'talk in great detail' about the McCann case.
It didn't seem to concern Busching whilst at the kite festival back in 2008, but when they were pissed in bar 9 years later & something about Maddie came on the TV, Brueckner turned to the subject again.
Busching was so horrified by Brueckners utterly convincing confession, that he waited until he got nicked for people trafficking before bothering to tell the police about it.
Of course, at some point Brueckner also told an undertaker that he murdered Maddie & destroyed the evidence.
It could well be that Brueckner really did abduct & murder Maddie, or, maybe he just took an interest in the case because he happened to live in the area, liked little girls & enjoyed chatting a load of shite.