There is a very good website on Bratislava Public Transport at:
http://imhd.zoznam.sk/ba/index.php?w=&lang=en available in both Slovak and English.
I have contacted the webmaster a couple of times and found him very helpful.
His address is ba@imhd.sk
http://www.mestskadoprava.net/galeria/index.php?/category/770 suggests that the bus is or was operated by
SAD Prievidza
http://www.phototrans.eu/15,77202,1151.html (Polish website) shows it was previously registered as PD-762BK
http://www.ikarusy.net/slovensko_ikarus_280/sk-partizanske-sad/236.html I think this means that SAD Prievidza retired it in Oct 2006 and sold it to the "Klubu historických autobusu Bratislava " in March 2007.
http://www.kha.sk/autobusy.html Has a spot for the 280 but no photo.
Regards
Michael Taylor
Binbrook, Ontario
http://www.michaeltaylor.ca