Rumour has it Go North East vehicles will have a 5 (or 50 for minis) added in front of their exsisting number. So for example......
730 - 50730.
3941 - 53941.
5525 - 55525.
6050 - 56050.
7142 - 57142.
8342 - 58342.

Apparently the vehicles would still change number if they would move to another fleet. So it remains to be seen if the vehicles are going to have these numbers applied or it's just going to be on paper / behind the scenes use only.