What about the issue of kol Isha (hearing a woman’s singing) in say a shopping mall or places where it is out of your control?

Kol Isha doesn't apply unless you know that particular female singer's identity and you also know what she looks like, which is usually not the case. Even in that relatively rare case, it's not your problem, for if they suddenly play such a song, it's considered "they came into my area, not that I came into theirs".