Most are removed and replaced with new equipment, and when a new building is supplied with a new electrical service lateral, they don't use this type of equipment anymore.
Many buildings here are remodeled, and the service "end box" is where these old wires usually land before the metering.
You can search on NSTAR the electric utility here and see what their rules state about these disconnects. http://www.nstaronline.com/
I am looking for information on these "old mains" and will appreciate hearing from anyone who has more information on them.
I have more images and will post them here soon.