It's a mixture. The railway is owned by the Ffestiniog Railway Company which has been in existance since the mid 1830s and is, consequently, the oldest operating railway company in the world. The share capital of the company was acquired by a preservation society (the Festiniog Railway Society) in the 1950s, after the previous administration had ceased operations in 1946. The first section reopened in 1955. Since then it has gone from strength to strength, rebuilding the railway from Porthmadog all the way to the slate town of Blaenau Ffestiniog, part of the route had been flooded by a pump storage HEP scheme so a new route had to be built (by volunteers). The 2.5 mile route included a spiral, the only one in the UK, and a new tunnel. What's known as the Deviation took about 13 years to build, opening in 1978. In the 1990s and early 2000s the railway set about rebuilding the Welsh Highland, 25 miles of railway through the Snowdonia National Park. Much of the rebuilding work and day to day operations of both railways is by volunteers but there is a core of paid professional staff - management, marketing, technical and operational. Boston Lodge Works has turned out four new steam locomotives in the last 40 years or so, currently working on two more and innumerable passenger cars and other vehicles. It's also restored or scratch built replica cars for other heritage railways and London Underground! To do that requires a core of professionals, supported by dedicated volunteers.
The Ffestiniog is one of the leaders in the heritage railway sector, but the model of employees / volunters can be found on a number of our other leading heritage operations.