ATA & NATROAD submission to parliamentary inquiry into EV transition, page-5

Full EVs have fewer parts, for sure. Hydrogen and hybrids are still combustion engines, so they have a similar or greater complexity to diesel trucks.
https://www.trucknews.com/features/electric-trucks-will-have-fewer-parts-but-there-will-be-maintenance/

I have a hard time seeing a shift to EVs being a net positive for SNL. One interesting exception to EVs requiring fewer parts is their tires - the extra weight makes them wear out faster, so this might be a new market niche that SNL could explore, but they haven't been interested in the tire business so far, and that's probably for good reason.

There are some big monied interests in Australia pushing for hydrogen trucks, instead of battery EVs - people like Andrew Forest with his Fortescue Future Industries. It remains to be seen how the economics of that will pan out, but if hydrogen trucks get widespread adoption in Australia then SNL's future seems bright to me.