On a holiday trip in the direction to Mostar, I stayed one day in the Tuzla area. This is, what was happening:

33 504 was shunting in the morning (approx. 0730 AM).
I asked afterwards for access. It was granted and the gatekeeper took my id as deposit. I stayed approx. 30 min close to the engine and received the id back after taking my pictures.
Tip for gatekeeper afterwards. Some asked for “Documenti” inside, but nobody hindered me in taking pictures.

33 503 was shunting in the afternoon (approx. 1530 PM).
I asked for access as shots from the outside seemed difficult and operation might cease soon. Access was granted, but only with a guide. The Loco was called, after 33 503 pushed all the cars through the facility; it was possible to let the train run through the facility again with many stops for photos. At the end of the track, the cars were uncoupled and I took a footplate ride to the “parking position” of the Sikule loco.
Multiple Tips, as many people were involved. Driver was customer-focused, that made an extra tip.
Great day! 😉