From the debate in the MUCforum it seems that the aircraft on the apron were provided with a set of stairs by the ground staff but no busses were available. Walking across the tarmac/apron to the terminal (thru snowed in & iced over surfaces) in the continuing snowshower would have been theoretically possible but was not considered as an alternative to regular bus service at 4am. The OCC of the airport and LH is staffed 24/7. The MRO of LH Technik is staffed at night and the airport (EFM) has 5 employees available at night who are trained to operate all ground equipment (who in this case provided the aircraft with stairs and put the chocks etc upon park).