Today I found a German article about Deutsche Telekom. Deutsche Telekom is still in the progress to remove their ISDN network. Sadfully it happens sometimes, that it is at a few locations not possible to offer SIP-Trunks as a replacement. It is technically not possible to have a broadband internet access that is VoIP ready. Such a situation is described in that article about the Hotel Haus Berkenbaum.
Even if it wouldn’t have helped in that special case, I recommend not to wait to long to check out alternative options to your ISDN trunk. To continue to use the older ISDN-PBX or to replace a smaller PBX I recommend be.IP Plus. In bigger installations I recommend Avaya IP Office. With it’s broad possibilities to configure a SIP Trunk it offers maximum compatibility to almost every carrier.