That applies also to Busses in Berlin. BVG gave their busses consecutive numbers, while the two first numbers identify type and production year.

However this is much more complicated than in Braunschweig. Here is an example:

3099 = 2003 (prototype, designated internally as 2004)
3101 - 3203 = 2005
3220 - 3322 = 2007

And so on.