That was lifted a good few years ago after the closing of the last deep mine. Harton Junction is the divergence just after Tyne Dock Metro. I suppose any of the two could be relaid, but they have talked about it for so many years, that's all it seems to be talk! I don't use the system, but from a neutral position, going the old route of the South Shields-Sunderland line would attract more passengers, and quicker.
I think the problem with reopening South Shields - Sunderland for the Metro is that it would saturate the line with extra traffic, in particular Sunderland station.