that is an interesting question. Given the fact that the allowable tolerances for lenses are quite a bit more relaxed in comparison to mirrors and also most designs work without aspheres, I would assume that most lenses are made more or less automatically like shown in here:
Very large and/or high quality astro scopes might get some hand retouching.
Even astronomic mirrors of quite acceptable quality (at least for smaller sizes, reasonable focal ratios and substrate thickness) are nowadays ground by machines in china - ask GSO how they manage this.
Very large, fast and/or thin mirrors of good quality are still the domain of a few artists, some of whom do some steps with machines but parabolizing is done manually there.