When attempting to place rails with command blocks, I noticed that I could not change the direction the rail is facing by using a data value. The rail's default behavior to line up with surrounding tracks takes over no matter what. Even when there are no tracks surrounding it, the rail is always placed with a data value of 0. As far as I can tell this does not happen with any other block.
Confirmed. Also this means you can't use it to place a normal rail going west-east. So it's not just alternate shapes, it's also the basic rail shape on the x axis instead of the default z axis.