The 750mm Ochsenhausen-Warthausen railway is a few kilometres from where I lived for about four years before coming to our current home. Typically, I didn’t go there when I lived close by.
The line was built in 1899 from Warthausen on the standard gauge main line between Ulm and Memmingen, to Ochsenhausen and then extended alongside the main line for a few kilometers to Biberach an der Riß. It crossed the main line on the level, like the Welsh Highland in Porthmadog, but that was removed after the war and the line now stops in Warthausen again, making it about 19km or 11.8 miles.
The line survived the war despite some bombing in Ochsenhausen and a severe accident on the crossing with the main line when a train travelling to Ulm ran through a signal set at danger and ploughed through the narrow gauge train at speed killing 12 and injuring a lot more.
The newly formed Deutsche Bahn took over in 1945 and did what they usually did with narrow gauge railways: ran down services while running busses in competition. To be fair this must have seemed a sensible option as the railway makes a large ‘U’ and the road was straight, but still. A preservation group took over in 1985, and had to close the line in 1991. A consortium of shareholders, mainly local governments and a bank, ran services again from 1996 until the line was closed by the transport ministry in 2000 because the track was such a mess. The local governments stepped in again, kicked the bankers out, and reopened in 2001, which shows the financial clout of local governments in Germany. In the UK it would be a cycleway by now.
The video shows 2-10-2 Class 99 tank locomotive number 99 788 bought in 2001 from Deutsche Bahn, who presumably were keeping it on the off-chance they might need it. Part two is here.
Information from Wikipedia Germany.