Apps, Trackers, Privacy, and Regulators: The Mobile Tracking Ecosystem [pdf]
eprints.networks.imdea.org
eprints.networks.imdea.org
Little to do with Android, mainly about 3rd party apps.
I think it's at least partly covered on page 2 under Uncovering Parent Companies :
> We obtain the parent organizations of these services (after accounting for business mergers and acquisitions) and identify the dominant organizations in the mobile ATS ecosystem. We find that Alphabet-owned ATSes have presence in over 73% of apps in our dataset. This raises questions about Alphabet’s monopoly in the mobile ATS ecosystem.
So alongside their conclusion that information is shared freely between subsidiaries:
> Our privacy policy analysis of the largest organizations revelaed the prevalence of intra- and inter- organization sharing of user data.
It would suggest that other large "players", along side Alphabet, could have much larger collections of user data than cureently understood. That would be my guess though.