The collaborative effort by ASCAP, BMI and SOCAN was announced with the following statements:
“ASCAP, BMI and SOCAN launched MusicMark to give our members a more efficient way to register their music. As of March 31st, 2014, publishers that use Common Works Registration (CWR) can submit registration files to all three organizations simultaneously via MusicMark, even if the work was co-written by members of different societies. Each PRO will then integrate the data into its repertory of works."
“We remain three distinct organizations, and anyone who uses MusicMark will continue to receive royalty distributions from each PRO individually.”
MusicMark shares more information in a FAQ pointing out the benefits:
A more efficient CWR registration process for our members;
More accurate copyright information available to music users;
A synchronized view of the works in our repertories, allowing us to resolve discrepancies more efficiently.
They also explain how to get started.
MusicMark states in their FAQ that there may be opportunities to involve other organizations in the future" but for now it's limited to SOCAN, BMI and ASCAP.