"Welcome to the Schengen-Area"
No Bordercheck at all. You enter the train at Salzburg like any domestic train as that is exactly what the Schengen agreement is about. Austria and Germany both signed the Schengen treaty similar to Italy and France.
The only thing that may or may not happen is a random passport/ID check usually on the train while itīs running.
But Iīd think thatīs a rather remote possibility only.
These sort of checks are normaly only done on certain occasions e.g. hunting for criminals etc. and as long youīre legally in the Schengen area (that Spain is part of) youīll just be fine anyway.
Thatīs not correct at the moment, there are frequent controls. But it will be done in the train and I wouldnīt expect any problems.
https://www.n-tv.de/politik/Deutschl...e20079620.html