Unfortunately, I've also been waiting for ages -.-. To answer your question, yes. It can be activated in the device settings and also depends on the provider, depending on the case.
PS: A quick Google search would also have answered your question ;).

So you don't know either ;)
Of course I asked Google - some say yes, some say no.

This depends primarily on the provider! Swisscom supports Wifi Calling. If the provider activates the function, the Mate 10 can also use it, otherwise not. Logical? You have to ask your provider, not the manufacturer.