Hi Paul,
I have several Strassenbahn photos in my collection and all show different variations of uniforms. I don't know whether there was any standardization of uniforms or whether each district/city used their own version.
The trams conductor in my photo wears the Wien Strassenbahn emblem on his cap. The person in the original post wears a similar type of badge. He wears all his gear for the photo including a lamp with white and possibly red lenses.
In his left hand he holds a whistle. My best guess is that he is some kind of guard. Which organization he was part of is unknown to me.
Cheers,
Larry