Initially, 5331 to 5338 were going to go on the X21 but, because of the major reliability issues on the X7 at the time given how premature the service was back then and the fact that single deckers would not match the needs of capacity on the X21, it was then decided not to put them on the Pronto.
But put it this way, I think we all know that the next round of orders will most likely include the Pronto. It's just down to the matter whether or not these will be cascades of a major B9 route or a new order of Street'Wrecks' (or Enviros if we're lucky).
P.S, happy to delve further into predictions if anybody is wishing to but over in the prediction forum to keep the mods happy please.
RE: Go North East: Latest News & Discussion - November 2015