Today, Film Music Reporter posted an article with all applicable details on the release, including the date, which is July 31st.
http://filmmusicreporter.com/2015/07/10/syfys-12-monkeys-soundtrack-details/
For those who are eagerly awaiting Season Two in 2016, here is a trailer featuring interviews with cast members and showrunners regarding the narrative arc of the next season.
http://www.syfy.com/12monkeys/videos/12-monkeys-season-2-preview