Deul, Thomas, thanks
Thomas, first of all - my fault, I need to precise it: I found Schweinfurt, not Bayreuth, as a destination with Regio120plus-Ticket
(beacuse half of us is starting from Bayreuth, the rest from Schweinfurt).
And
they say here:
Mit beiden Tickets können ausschließlich Nahverkehrszüge in Sachsen, Sachsen-Anhalt und Thüringen sowie auf einigen Strecken außerhalb der Ländergrenzen genutzt werden.
The
"Streckenkarte" shows Berlin and Schweinfurt among external destinations, so it looks like a suggestion, that Regio120plus-Ticket also works there. And bahn.de seems to confim it by suggesting that type of ticket between Berlin and Schweinfurt.
Ufff, guys, thank you very much, I think I know everything what I wanted to know
Have a nice day there.
Szy.