Not a leak but a true doc dealing about Bell Beaker mtDNA: Roth, Christina,
Once upon a time in the West : paleogenetic analyses on Mesolithic to Early Bronze Age individuals from the Iberian Peninsula, dissertation, Univ. Mainz, 2016
some points that are worth to mark:
p.33 the author is providing the mtDNA haplos found in Ukraine and steppes... no characteristic regional mtDNA is found in Iberian BB, so that whichever Yamnayist would try to link this culture to IE is left with few alternatives as the steppe warriors came without their women (no mtDNA), the warriors were selected taking into account their mtDNA (not eastern mtDNA were allowed), and they did not left any track in archaeology (no steppe cultural traits in Corded Ware and much less in BB), so that the unique way left for the steppe warriors was traveling by sea (surely riding sirens).
p.90 BB of Central Spain cluster with Portuguese Calcholithic
p.135 the author thinks that the genetic difference between Central Spain BB and other contemporary Iberian groups points to a migration, discarting a simple "pots difussion".
p.147 and 150 no genetic relation between Central Spain BB and Central Europe BB, but there is an Iberian connection with high H mtDNA groups and with the appaearance of H3. It's quite important to know that the Central Spain BB arrive there at the same time as BB in Central Europe.
the most good point is in page 148 "Genetic evidence so far can therefore dismiss an Iberian origin of the Bell Beaker phenomenon with demic distribution into Central Europe -at least on mitochondrial level; one will have to await what Y-chromosomal or autosomal ancient DNA data will show."
the case with mtDNA freq data alone is problematic: haplos are old enough as to have refugied after glaciations and expanded after warming, and haplos are old enough to have traveled along major migrations, but also step by step after so many millennia by marrying non locals and/or by considering women as a good to exchange.
Just empirism could show the case of mtDNA freqs quite well: surely the mtDNA freq in Spain, Chile, Bolivia and Ecuador will be quite different, but such differences couldn't tell anything about the common language used in such countries, or the freq of R1b there.