The copies of the 4th Shiritsu Holitsuba Gakuen Drama CD are already being delivered to their respective owners in Japan.
The CD was a special privilege for those who purchased the OADs of XXXHOLiC Shunmuki and Tsubasa Shunraiki. The Drama CD script was written by CLAMP’s Nanase Ohkawa.
Here’s a picture from the package and booklet:
No downloads so far, but I will post here in case they show up =)
Update: More pictures in the comments.