The model, introduced early 1994 (UL70 series also called U412-220 UL70) and produced until 2002, was mostly used in Bucharest's bus network operated by RATB even though some U 412-260s are also used in other Romanian cities such as Braşov, Cluj-Napoca, Galati, Craiova, and Oradea.

STB has withdrawn all of them from service (including trolleybus 7454), because some of them were severely worn out, but also because RATB wanted to operate solely low floor busses with air conditioning.

RATB removed Rocar De Simon buses from operation in mid to late 2011.

Rocar De Simon was quite a modern vehicle at its time, actual design, having MAN Euro 2 engines, automatic transmission (although vehicles with manual transmission also existed), ABS, electronic controlled air suspension (ECAS), tubeless tires (although some were delivered with tube type wheel assembly), Fluorescent lighting of the saloon, plastic (sometimes with upholstery) seats, Blaupunkt sound system with public address with bus vox system announcing the stations, electrical ventilating rooftops, heated saloon, STOP button in the saloon (for announcing the driver to stop at some desired stations) and some safety features (like hammer for crashing the windows in case of fire), and many of them were equipped with electronic display (few of them were even equipped with luminescent display).

Body parts like panels, glasses, tail lights and headlights could be brought from Italy or other countries which were operating De Simon Buses.