QR has had a pretty intensive timber trestle program underway for about twelve months. In the 2015 state budget QR received $75-million for a bridge renewal and replacement program. To date most of the work has been focused on the Central Line west of Emerald and the Clermont branch. The Western Line has had a significant bridge replaced at Oakey and there's a few more big trestles on that line about to be replaced. As for the North Coast Line, at least one was replaced last year south of Cairns. These bridges are definitely life expired, but there hasn't been much of a rush to replace the few remaining timber trestles on the North Coast Line until now (possibly because they'd already been strengthened for 20-tonne axle loads).
Back in the 1990s when the North Coast Line was upgraded to 20 ton axle load the scope of the project was to replace all timber bridges and replace all curves less than 80km/h where possible.
The standard was for 120km/h alignments where possible.
However due to changes forced on us by politicians the budget exceeded the original estimate.
The majority of timber bridge replacements were those that were on straight track with reasonable vertical alignment.
Those in areas of substandard horizontal alignment were to be replaced in the future.
Then some brilliant project manager worked out the costs of just replacing these bridges without only a small allocation of funds for deviations.
So we now have bridges being replaced "online" without any improvement to the horizontal alignment.
In some cases retaining the 50 and 60 km/h curvature of the existing alignment.
All this on a line where the allowable top speed for freight trains is 100km/h.
Both Killymoon and Sheep Station Creek ate close to low speed curves and I would be surprised if any improvement in horizontal alignment is proposed.
Building a new bridge in these areas would preclude any future speed improvement.
Queensland Transport who is the final authority for these things would not contemplate this sort of expenditure on the Bruce Highway.