when you start an mission,you see the CI original tracks. Why not using your own tracks?
It can be done if you modded the game.
Because that’s how the game works now: most of assets were taken from CI3-5, even some new enemies. It’s possible for new soundtrack to appear after release but it’s not that important during early access state.
The only way is through modding
or you can just turn game music off and play your own music from youtube.