Wow, every since BMR (BuildMyRank.com) got booted down, lots of Private Network questions are out there. In simple words, private networks specially when owned by the same person and / or link to the same network of sites are identifiable by automatic algorithms (Think what those Phd's are doing at Google).
Also, you might want to read these similar questions 1, 2.
Keep in mind, you are still prone to risk and whois protection or not, if a human can find it, patterns in linking can also help them identify themselves as networks. Moreover, if these sites are not strong themselves, how are they going to provide value ? so now, you will have to worry about getting links for those 30 sites as well to strengthen them. Otherwise, if there's no inbound links to those 30 sites, there's not much link juice they have to pass.
Makes sense ? I hope that helps.