All of Apple's previously paying Beats customers are in the 3 month free trial. Once that trial ends I'll bet those customers continue paying. I know I will.
When Apple acquired Beats Music, it was "believed to count just 300,000 paying subscribers."[1] That's about 3% of the current total Apple Music subscribers.
Yea, those were the reported numbers up to the end of December. I'll bet that their subscriber numbers started going up after that as users joined following Apple's acquisition, I know I did.
[1] http://appleinsider.com/articles/15/01/12/apples-beats-music...