You were talking about issues for cyclists because of diverting car traffic, or did I misunderstand you? Mariahilferstraße was a real traffic hell. On maps it might have been classified lower in priority but if you had seen it in the good old days, the main difference was that it had less throughput in cars because it was more traffic jammed than other routes.

That said, Camden High Street appears to be a 4 lane road. So that is indeed somewhat worse. So kudos for the planners that they are doing something about it. Of course there should be supporting actions but they certainly shouldn't be relocating traffic or making other streets worse.

I don't have any data but yes, it would be interesting to see what the 18 month test run was doing to traffic patterns. If cyclist routes had been really impacted, actions should be taken to upgrade cycling infrastructure, or priority in the cylicing/car mix of modes along key routes.