Do you know the AMC Lincoln square theater? I was involved in the construction of that place. Ten escalators that I can think of, including, at the time, the longest unsupported escalators in the city. All one company, all installed pretty much at the same time. Contractors did everything else- all the escalator guys had to do was install the escalator into the space provided by the contractor. Despite different lengths and widths, it was all pretty straight forward, and even the free standing unit was off the shelf stuff. I didn't personally work on the escalators, but I remember them showing up in crates and getting assembled pretty damn fast. The four story free standing ones were the only units that took over a week to build.

The guts looked for all the world like giant erector sets. Build the frame to length, choose the right size motor, assemble the links in the stair chain, cut the railing to size. It seemed pretty universal to me, and quite the opposite of bespoke.