You are missing the point in blind hatred of Burnham. I think he's a shameless self-promoter, who spends too much time traveling the world rather than fixing things here that have been under his control all along, like the trams.
I was trying to describe it in another way. You are correct in that the government did not tell GM (it's not a Mayoral decision anyway, it's all the authorities) that we had to bring in a chargeable CAZ. They did tell us that we needed to improve air quality to a specific level by a fixed date and none of the modelling showed it could be achieved without effectively banning the most polluting vehicles.
And whilst the order came down from central government, it was actually due to a requirement on the government that they just pushed down to various local authorities, including GM.