The original phone booth was demolished in the 1970's. I can recall passing a small pile of rubble at its location running west out of Antonito. About the only thing recognizable was an intact window frame.
The FOCTS gang have built a replica phone booth out there now. I saw it when I was running the Eureka last month.
The only real evidence still visible concerning the siding is there is a stone culvert that goes under the track mid-siding. The culvert extends out from the mainline an additional 20 or so feet because it went under the siding too.