Think about how much material insider info they would need to get their returns on their AUM. Then think about that on the timeframe the Medallion fund has been in existence.
For people who may not know the figures (these are from memory): In 30 years, Medallion has had only 1 down year, when they were down by 4.5% (this was around 1988 or 1989). In their entire 30 years of existence, they have averaged over 34.5% annual returns. Averaged.
I don't think that you would need that much insider information--you can just use more leverage. As a thought experiment, it's possible to earn similar returns by wiretapping any large business newspaper.