The same applies to traffic signal and data engineers on our highways networks. These too often involve complex wiring (copper and fibre), bespoke hardware & software. Like railways there are not a lot of skilled people available to design and install the kit with the technology firms (often the same that do railway signaling) constantly cutting back, reorganising and reducing capacity.
Off / on spending in this market seems to work against training and recruitment, as capacity goes down, prices go up....