Appointing independent firm isn't new, its standard procedure of all ADB and WB projects. They are called consulting companies, appointed to ensure the quality of the work by the contractors, basically according to FIDIC Laws developed by these banks. But they generally works in between the Govt. And the Cpntractor. This is all over the world even in European projects. But what's new is the following part:
the independent firm will not be under the government or any co-financier of the bridge project. It will make its recommendations independently, and the authorities concerned will implement those
So the government/contractor won't be able to do corruption and steal money, since ministry can't pay until the consultant approves. If the consultant would work under the Ministry, ministry had enough power to manipulate the consultant, since consultants payments are subject to again ministry approval. We know why WB is coming up with such conditions. If govt is sincere with the project, why can't they accept it?