Cum adică unele sunt "în curs de păstrare"? Se pregătesc să fie păstrate pentru ce?

Probabil s-a referit la conservare.

Trei fotografii din trecut, când aceste autobuze rulau pentru Wiener Linien.

8851 pe linia 62A pe Eichenstraße în Ianuarie 2007
Autor: Peter Bures


8935 pe linia 15A la Altes Landgut în Septembrie 2010
Autor: Peter Bures


8951 pe linia 13A la Südbahnhof în Ianuarie 2005
Autor: Łukasz Kuczewski

Hi,

someone know at which time and place I can see the Gräf Steyr busses?

As far as I can tell from the thread, there's a lone survivor that is fully functional and should be in service on the standard bus lines in the morning, alongside the "special" lines in the afternoon.

I doubt that you will find it during the holiday period to be honest as across Romania there's the holiday timetable in effect.

Ah okay.
Is it a regular shift, I mean is it every day the same line and time?

No, the Graf Steyr bus can usually be found on line 2 in the morning, but it can also be on line 4 or 5 (but that's not common). If you go to a central station like Str. Franceza in a morning workday you can find it since all three lines go through that station.