I based my comments on a report I saw some time ago comparing the BBC with ITV regarding the numbers of staff sent to cover the Olympic Games.
A premise, that while factually true, is missing the key factor that the BBC have the rights to broadcast the Olympics, while ITV do not. It's like asking why the BBC sent more people to the Olympics than my local newspaper, or why there are more bus drivers in London than my village. You're not comparing the work that those people are doing, just the raw numbers. Therefore your comments are based on a fallacy, and your conclusions are therefore invalid.
I can guarantee that ITV would send more people to the Olympics than the BBC of they were the rights holders instead. Being a commercial company has nothing to do with it (indeed, you should see the numbers the Americans send over).
I realise that high quality video didn't need to go between every location, even on a live production, however, even the talking heads of presenters and guests at home (as sources of some video) seem to have better quality images than can be got back to the broadcasting centre by anything less than a very good FTTC or FTTP link, and there would be a penalty of delay that comes with any compressed video where the GOP is large enough to squeeze it into a compact stream that adds onto whatever the IP routing causes. So I presumed that it would be intra only compression. I must admit that I had forgotten 4G, (and indeed 5G if it is usable anywhere yet), so maybe if a genuine 50Mb/s+ can be reliably supplied as an upload, and GOPs reduced to the minimum, it is just do-able, especially when there is a commercial imperative at work.
The latency of the high bandwidth feeds (5Mbit is usable, 10Mbit starts to be good, 50Mbit is higher than would be sent over satellite for a primary programme feed) is less of an issue, as long as the timings stay consistent as you can delay feeds appropriately where you put them together. You can use simultaneously a low latency feed at much lower bitrates to give you confidence / talkback / return video feeds and reduce delays between participants.
4G connections have become fairly standard for remote inserts, primarily in news, but also other programming. I believe the Timeline kit being used by BT Sport was originally bought for coverage of women's football, with all the production happening at their base and all cameras fed back over 4G (most matches are single camera jobs).
Basically the clever bit is the linking up of the various technologies that have become standard over the last few years in different areas of broadcasting, and then translating that to having your production staff in separate locations as well as your contributors.
The BBC is still very much into ISDN for audio and much of the current news output relies on presenters using ISDN mixers at home, so presumably, their personal phone lines have been converted to that, or they have managed to get some extra lines installed at short notice.
The BBC have also been using a lot of IP connections over standard broadband connections for their radio broadcasts, using software like Luci Live.
As I said before, Openreach have stopped going on to customer premises, so an upgrade or new line isn't going to happen at the moment.