Are only authorised vehicles allowed to stop in the place marked with this stop line?

Why?

Beside the visible shelter, the P-17 bus stop marking identifies where vehicles authorised to use the stop may stop. Other vehicles must not stop voluntarily anywhere along the marking. This includes stopping briefly to let a passenger out.

§ 90 ust. 1 rozporządzenia w sprawie znaków i sygnałów drogowych, P-17 „linia przystankowa”