There is a dedicated thread for soundtracks of mobile games, it would be nice to combine all the (so far few and scattered) efforts in one place.
Encrypted ogg files are not uncommon so finding and sharing a potential solution would be nice progress (it very likely involves knowledge of the tools used in development as the files don't give any indication of the encryption used).
Just tried something. I put a Fire Emblem Heroes .ogg in Super Mario Run, and it played fine, but when I put a Super Mario Run .ogg in Fire Emblem Heroes, there was only silence.