They already run similar systems for traffic in some cities. Bangkok being one that I’ve been to. They have toll roads in the sky, and also the sky train (which is a little bit scary if you ask me). So I see no reason it can’t work for bikes, so long as there’s enough traffic. And it seems to be in abundance in London.
That said…whilst I’m all for segregated cycle facilities, I can’t help but feel it’s a bit ‘out of sight, out of mind’. And I think the city would actually be much more pleasant if it was full of cyclists and pedestrians at ground level, and you put the big noisy motors in the sky somewhere. It feels the wrong way round.