Even if there is already a road in place, you should probably hold off on uploading any of these until the big NZOGPS road and LINZ railroad layer merge has happened.
You may need to individually merge these with the road/rail/trail that the cutting is parallel to. Keep cutting=right if the cutting is only on one side of the road (from the perspective of the road in the direction of the cutting's way), tag with cutting=yes if you are merging two cuttings into the way, then remove the decorative cutting ways. Remove the fixme tag once done, or if unneeded. E.g., if the edge is a terrain feature of its own and merging with the road would lose information. (in these situations adding natural=cliff to those might be appropriate).
If there is no road/rail/trail there yet then leave this with the fixme tag still there and it can be cleaned up later.
much like a bridge along a way, tag the section of polyline with cutting=yes.
LINZ: "An excavation of the Earth's surface to provide passage for a road, railway, canal etc."
although they probably don't apply here.
HB: we'll have to test to find out, but probably these are offset from the roads, not part of the roads as the osm cutting=yes assumes. there is also cutting=left|right to consider if direction of the feature is known. [it is, use cutting=right]