(01 Nov 2013, 2:26 pm)eezypeazy wrote Interesting speculation...
In the Voluntary Partnership offer from the bus companies, there's a table headed 'Euro engine standard of Tyne and Wear fleet'. That shows the number of Euro II, III and IV engined buses falling, being replaced by Euro VI-engined buses in the main. The implication of this is that the three big operators don't envisage second-hand replacements for existing buses that operate in, or into, T & W.
I suspect the days of 'cascades' (out of London in particular) might be numbered, especially as partnerships in other conurbations seem to be delivering new buses, too.
or the engines are retro-fitted with catalytic kits, up-rating the engine and Euro spec as has been done previously and likely to happen in the future too...