A source would be kinda nice. Not because I doubt it's possible, but simply because I haven't heard of it.
edit: I'm trying to make that more clear. The difference is that right now, they are not forced by law to collect those data, hence the penalty and lawsuit from the EU. But they may do so - and that is done in practice -, and there is a law that if they do, law enforcement can get access.
And who claimed it hasn't? I didn't.
You said "the data" is being collected anyway. This, without any further elaboration, seemed to imply "the data that the EU data detention directive would cover", and not "the data ISPs collect to enable their operations".
I think the difference is that if an ISP wants to collect as little as possible, and anonymize/delete any data they don't absolutely need anymore, that'd be legal; If the police wants it 12 months later, they can just say "sorry, we don't have it anymore", provided that's truthful. Under the EU data detention directive that's no more, as not keeping the data for at least X months would be verboten.
You did, in a way, with
> No, it was being collected, until the Bundesverfassungsgericht put a stop to that
Have a look at http://www.datenschmutz.de/moin/TK-Verkehrsdaten as to which data are currently saved and for how long, keep in mind that the mentioned numbers are old (but realize that collected Bestandsdaten includes data from people with flatrate, which would never be necessary for billing purposes).
