are there any shortlines that still use motor cars or speeders for track work or inspection?
The Portland & Western has a speeder still in use for a track gang.
The Willamette Shores Trolley has a couple of speeders. I know the Oregon Pacific RR owns a speeder but I don't believe they typically use it (however they have hosted public speeder excursions; it's actually the only railroad I've ridden a speeder on myself).