It was not an easy job, but the plumber finally cut a section a section of the sewer pipe out.
The clog was not in the section of the pipe he cut out as the scope had suggested, so he roto-rootered both sections of the pipe and was able to clear the drain, which saved us cutting more of the slab and digging another hole.
As an interesting archaeological aside, paving bricks were removed when the hole was dug out and what looks like a curb cut is in the upper left-hand corner of the above photo. The front part of the building was built in 1894, and the back part of the building at some time after 1894. It's possible they build the addition right over a street or alley, which would explain the pavers and what could be a curb cut.
Crappy foot prints out the back door.
A sample of tools used by a modern day plumber.
The solution — a double clean out.