It was not just sitting, but being renovated, albeit very slowly. The series 200 hubcaps make it look even older.

Even better :D Interesting though that Promet Sinj doesn't seem to have an individual livery, I guess they're just a subsidiary of Promet Makarska?

Yes, they are owned by Promet Makarska. Basically, they are the terminal station for fossils and rejects from Makarska. What happened was that in 2005 Makarska bought Autoprijevoz Sinj. In the contract, they agreed to buy a fair number of new buses to refresh the company, which was in debt, but still operating. What they instead did was loan them their older buses. Slowly, they killed Autoprijevoz (whose buses were white with a yellow stripe, hence the logo) by scrapping their old vehicles, taking over their lines and, most importantly, infrastructure (bus station in Sinj). As there were some legal problems, in 2013 they just transferred all buses to a new company they formed, Promet Sinj. However, no actions were taken because problems can just be swept under the rug when you know the right people.

Ohh okay. Thanks for the clarification, by translating Croatian forums I usually only understand half of what's going on, especially with the lack of background knowledge :)

I understand. You should translate to English if you know it well (seems you do), it will get the best results. So, yeah, to be 100% correct, almost all vehicles listed for Promet Sinj here should be under Autoprijevoz until 2013.