On the current alignment, the Kingaroy Branch will never be re-opened; there's just too many tight curves (down to 100m radius in some places). There's one spot (can't remember where) where the railway goes through a cut, follows the ridgeline in an 'S', curves across an open field, crosses a substantial bridge, then does a hard left-right turn (EDIT: It's not quite as I remembered it. It's worse. Check out Google Maps of the Nodinga/Oakview section. Mouingba is also a surprisingly sharp - but brief - grade). If the branch was reopened, the entire section from the cut (which has other alignment issues on the far side) would be straight-lined, with a new bridge. Doable (it's just rocky cattle country), but not cheap, and the local landholder (who came out with 'support' to see what I was doing) is unlikely to be keen to have his pasture cut in half again.
Leaving even a rail fish plate behind falls under littering and they can be fined separately for each individual piece and in the case of a railway this could be $10,000's over a few kim if they were not careful.
The company that ripped up the Kingaroy Branch should lawyer up, then, because when I walked it, there was debris everywhere.