Additional info: According to a German news article [1], this affects more than 100 developers/companies who provide XMPP client software. In their view, these count as "telecommunication providers". The interesting bit is that they explicitly point out part 7 of the TKG (telecommunications act) which details the telecommunication provider's duties in assisting law enforcement agencies, such as providing interfaces for targeted surveillance.
[1] https://www.golem.de/news/meldepflicht-bundesnetzagentur-wil...