(26 Jul 2020, 4:27 pm)streetdeckfan wrote Will the generic X-Lines be allocated to the X21 straight away in replacement of 6331/2?
Not immediately. They'll be used for familiarisation for a couple of days first (on paper, at least).
Chester-le-Street have float OmniDekka 6143 covering for 6331 and the usual school holidays PVR reduction provides an OmniDekka to replace 6332.