Things have probably changed since I last talked to my friends at a large state radio/tv broadcaster, but for long haul they used either MADI over fibre, or AES50 into boxes from NetInsight along with SDI for the video feeds. This works so well that you can put the input/output converters in a venue hosting a live music and do the program audio mix in a control room at broadcast HQ 100s of kilometers away.
At 100s of km, you’d be pushing the limits for actual live sound, though. 100km is about a light-millisecond, and ordinary fiber is rather slower than light, so that’s maybe 3ms round trip per 100km. If a musician can hear themselves through monitors at too much more latency than that, it could start to get distracting.
As i understand it, the sound for audience in the venue and monitors for artists was run locally by separate mixer. The audio backhauled to HQ was for the live broadcast.
