Bowie is spirit-network-resistance-prophet Boz ("The most famous pirate on the Multiplan. He knew the network by heart and got a sly pleasure from foiling Ix's attempts to identify him." to quote the wiki) but also appears as part of a music band resisting censorship laws called the Dreamers, performing several songs made for the game, that you can catch in secret concerts. I don't know if the game explicitly suggests Boz and the singer are perhaps one and the same.
I think they're not, I think that's the goofy thing.
Iman is in the game too, she's an assassin or something

that whole game is just so fucking weird (I mean just look at that sentence you quoted lol), but it holds together better than when Cage started combining his weird shit with the real world
although I certainly don't remember it
playing well,
Fahrenheit was quite a bit more polished on that front