I just looked at the journey history for route 8 on bustimes.org earlier today. The 0613 from Bolton arrived into Shudehill 10 minutes early despite passing through that junction. So when there is little car traffic, buses aren't delayed. Therefore it is possible for buses to be on time and if there weren't any cars they wouldn't have to spend money improving that junction. Cars are the problem.
Oxford Road is mostly buses only so presumably some cyclists don't feel too scared of riding in the road. You can't extrapolate to every cycle path in the world. Have you actually investigated in detail how cycling works in the Netherlands and Denmark? In London, where cycling is more advanced than in Manchester, many cycle paths are heavily used, so much so that there are often queues at dedicated cycle traffic lights.