You can download it from here: https://support.microsoft.com/en-us/kb/3061064
This is some of the new features that is included in this CU:
The June 2016 cumulative update adds the following new features to Microsoft Skype for Business Server 2015:
- Video Based Screen Sharing
- Multiple Emergency Number
- Busy Options (Busy on Busy and Voicemail on Busy)
Busy on Busy has Competella delivered in a long time with their Competella Routing Agent. What Microsoft has published in their, am I at present time not sure of. But it will be testet and I will come back with a blog about this.