I'm pretty sure the line wasn't that close to the hill, check the 1966 map - it has the old highway route in between the line and the hill just before it crosses the line.
Thanks for your opinion as we were just curious as it was one of the few remaining bush areas, especially as you surprised us with the earlier Alison Rd one. I did not think to check around Alison Rd yet the cutting was sitting there waiting to be revealed on Railpage.
The following post is a 1917 map of the area.
Just doubled checked and Hairyleg's plot goes straight through the bush area in question, the green belt western side of hill along Spencer Rd between Pappas Way and John Francis Drive, cutting #4 on WPS. I still think it is worth a check. Hairyleg is usually correct on this route, allowing a few feet either side as shown at the Kirra Cutting and the Currumbin Creek bridge areas.
I wonder if the 1966 map may have been an older highway location and the highway relocated since then? That 1966 map in that area is a little like the 1917 version I also posted.
I would not take Hairyleg's plots as being 100% exact as to location on the photomaps.
They are from various sources and are dependent on the scale and accuracy of the original maps.
Then one must allow for slight inaccuracies in tracing from large scale maps and then expanding the plots to real world co-ordinates.
A small error can thus be magnified by the scale of the original map.
In some places the I found the QR North Coast Line plot is about 20 metres from the one in the photomap.
When querying this with the person responsible for the mapping I was told that Google Earth maps are not always correctly georeferenced, which is understandable considering the magnitude of the task.
Please do not take this as criticism of Hairyleg's efforts as I have great admiration for what he has done, but injecting a bit of realism as to the ccuracy of the mapping.