[mb-users] Unreleased Soundtracks

Good day,

I've a question to unreleased Soundtracks. My specific case is the Movie 
Cellular.

For this movie exists an official score:
https://musicbrainz.org/release/cfb0b658-5c92-4617-93f5-8d5274b399b8

Indeed, I cannot find a released version of the Songs that are played in the 
movie and are listed in the credits:
http://soundtrackcollector.com/forum/displayquestion.php?topicid=3439
http://www.imdb.com/title/tt0337921/soundtrack

I would like to adding these songs to MusicBrainz. Does a predefined scheme 
for such cases exist?

Kind regards,
Gerion