“I’d like to see exactly what sort of (wall|fence|barrier|whatever) they’re building”
They call it “wall system” - a combination of 18 to 30 foot steel bollards, with good patrol road, cleared observation areas, sensors/alarms, and in some cases fixed cameras and stadium lighting.
In the Rio Grande Valley, much of the new barrier will do double duty as FEMA hurricane-certified flood control levee, requiring pretty massive concrete foundations (which drives up costs there to about $25 million per mile).
It is basically the top of the line of the Border Patrol’s wish list - solid, effective stuff that will stand for many decades - likely a century or more in the desert.
That’s certainly not going to go in as fast as railroad tracks.