(01 Jan 2014, 7:24 pm)tyresmoke wrote Or the 4 red B9's and 3 Citaro's (why does X7 justify 4 branded buses yet every other brand gets its PVR branded only?)

This is not always the case. Often the way cascades work, you're very limited - you can't always have like for like replacements on services. Where possible, a spare bus will be allocated. A lot of services do have spare vehicles, whether they are branded or not.
A great deal of time, thought and effort goes into the future fleet position in preparation for new vehicles entering service, and deciding the best option whilst considering cost and suitability is - no doubt - quite difficult, and involves several parties of whom may all have different ideas.

In regards to the X7 specifically: Although we have no guarantee that four vehicles will be allocated to "Wear Tees Xpress" service X7 (we're going off suggestions that the X7 is in-line to receive an upgrade at the same time as Citaros becoming available), it seems appropriate to perform the usual "like for like replacement" regime, as it is possible to do so.
I have noticed that vehicles are often taken out of service after their first run on "Wear Tees Xpress" service X7, and they go out in service again the hour after. I have assumed this is linked to more economical refuelling arrangements at Deptford depot, though I am not positive.
I guess Cadets will be the only spare vehicles after the upcoming fleet position changes, and downgrading from a higher class Citaro to a lower class Cadet is not ideal at all. If the Citaros are to remain on the service for a long time, why not give it a spare to guarantee that the service will run as smoothly as possible while maintaining all high standards set?

One possibility, in addition to one Citaro heading to Riverside to be branded "Blaydon Racers", was that one of the '06-reg Citaros could be repainted red to act as a spare for both the "Blaydon Racers" network and the "Crusader" 27 service. Both services justify a spare vehicle (having PVRs over 8), and it would mean that their allocation could remain more consistent, with less chances of older "Northern" branded vehicles appearing. If this was the case, surely the "Diamond" could be in line to receive a similar red liveried vehicle to act as a spare.
If the "Lime" does get Citaros next year, Stanley depot and Chester-le-Street depot should each have one 'red spare' vehicle.
The idea behind depot standardisation of vehicles is great. If Stanley depot was to become "Citaro-standardised", they'd have a lot of flexibility in regards to the allocations if there were to be multiple red spares.

As we've already discussed, future orders should receive one 'red spare' per eight vehicles to allow the vehicles to be used on other services when they're not required on the branded service it was purchased for. This allows for the greatest flexibility when it comes to allocations, and the eldest members of the current 'red spare' fleet can be phased out gradually.

The "Cobalt Clipper" and "Fab Fifty Six" both have a PVR of 15 but have proven to be fairly challenging services with vehicles being out from very early in the day to very late in the day. In addition to this, both services are "high performers" and could quite easily justify the cost of two spare vehicles. You'd be daft to give up those spare vehicles to the "Pronto", when it's entirely plausible new vehicles could be purchased next year if plans were to change in regards to the current 2014 order prepositions we've discussed elsewhere on the forum. Who is to say that Go North East will even stick to 80 buses? Eight extra vehicles purchased in 2014 and taken away from the 2015 order isn't too bad, after all...