I came up with this after about 5 minutes of fiddling. You can make the spine this way without having to resort to the Construction Kit, NL1, math, and all of those bad things. Gerstl either used the construction kit or some voodoo to remove the diagonal crossties.
1. Make your track
2. Save it as an element.
3. Paste it on top of itself
4. Sink the heartline down
5. Spam "simple" track connectors equidistant and connect them via pipes
6. Set the track as invisible.
7. Repeat steps 3 through 6 for an additional track, and sink the heartline even lower.
You should end up with the hideous abomination I created below when you're done.
The heartline sinking process preserves radius scale, which is nice so that keeps you from going through radius change hell, which would happen if you tried to copypasta supports.
Perhaps someone could create a triangle track with no crossties by setting 3 two tube spine tracks offset and lowered from the original and adjusting the banking by 45 degrees in opposite directions. That's something I'm not willing to try but perhaps an adventurous type could while avoiding reverting to NL1 and the Construction Kit. Remember kids, eventually compatibility mode won't save you down the road if you're trying to run old programs.
The spines in the image I posted aren't scaled correctly at all, but you can get the general idea of it conceptually from my pic. Each color represents a different track used to create the look.