[TheHippo]

I don't know. The Berlin train system is known for stopping to work if its either to hot, to cold, to windy or to rainy.

[tehabe]

This is about the subway (U-Bahn), not the rapid transit (S-Bahn), the latter had serious issues with maintenance a couple of years ago.

[nealmydataorg]

I recall that before unification(in West Berlin) S-Bahn trains used to be older and U-Bahn trains were newer. I do not know current state of comparison between U-Bahn and S-Bahn trains.

[tehabe]

The DB bought newer cars in the late 1990s, the class 481. But this class had a lot of issues, which could be mitigated by better maintenance but since the DB wanted to go public those costs were too high, so they cut spending on maintenance.

And so the 481 will be replaced by the 483 and 484.