What are you talking about? The signal coming from a live event is the full package. The output of “the truck” has multiple outs including the full mix of all grafix, some only have the mix minus any branding, etc. While the isos get recorded in the truck, they are not pushed out to the broadcast center.

All of the “mixing” as you call it is done in the truck. If you’ve never seen it, it is quite impressive. In one part of the truck is the director and the technical director. The director is the one calling things like “ready camera 1”, “take 1”, etc. the TD is the one on the switcher pushing the actual buttons on the console to make it happen. Next to them is the graphics team prepping all of the stats made available to the TD to key in. In another area is the team of slomo/replay that are taking the feeds from all of the cameras to recorders that allow the operators to pull out the selects and make available for the director/TD to cut to. Typically in the back of the truck is the audio mixer that mixes all of the mics around the event in real time. All of that creates the signal you see on your screen. It leaves the back of the truck and heads out to wherever the broadcaster has better control