Interesting and I'm sure you're probably right.
I'm not sure what system is used on the 11, but generally the on vehicle equipment is simply a box attached to the roof of the vehicle - very easy to swap from one bus to another - in this area Arriva often move odd buses in from elsewhere in the country and others out, and they have to have the bus priority traffic signal trigger/real time GPS system boxes swapped/installed. Looked at from a high vantage point, it can be seen that some vehicles have two or three of them - presumably it's cheaper just to add the relevant box rather than swap them.
I'm not sure what system is used on the 11, but generally the on vehicle equipment is simply a box attached to the roof of the vehicle - very easy to swap from one bus to another - in this area Arriva often move odd buses in from elsewhere in the country and others out, and they have to have the bus priority traffic signal trigger/real time GPS system boxes swapped/installed. Looked at from a high vantage point, it can be seen that some vehicles have two or three of them - presumably it's cheaper just to add the relevant box rather than swap them.