In my country there are regional centers, 15 of them. When you dial 112 to get in touch with them and there's a too long waiting period, you could end up talking to another regions center that have no local knowledge. But initially that's not necessary as the local forces that are dispatched have all the knowledge they'll need.
I believe all EU public safety are digital encrypted Tetra besides one or two countries (France) that are digital encrypted Tetrapol, which only have part of the name common with Tetra and everything else are a totally different system and uncompatible. We have full interoperations with our neighbouring countries and have regular exersises to check that everything still works and haven't been compromised by upgrades or from other maintanances on the systems.