Also keen to find this out re updated ACE exam for LR6/CC
ACE's are not updated for every version. Since LR6/CC2015 has been released quite some time ago, I believe the next update to the LR ACE will be for LR7/CC2016.
The ACE exams were updated for every major version. However, since the move to Adobe Creative Cloud and the subsequent handover of the writing and management to Pearson VUE / Certiport, the Adobe Certified Expert programme has been up in the air. You will NOT find the right answer to your question. The people who know it are under an NDA!
BTW, the CIAB series is not written specifically to help you to prepare for the ACE exam (though it is publicised in places as such). It can help, of course. It's actually written to help you to learn Lightroom.
On the other hand, we at Examaids Ltd have created standalone, interactive applications for Windows and Mac OS that can help you to prepare for the Adobe Certified Expert (ACE), and the Adobe Certified Associate (ACA) exams, and we shall be updating our Photoshop Lightroom 5 ACE Exam Aid to whatever version Pearson VUE / Certiport release in the coming months.