Huh. I had no idea there were "shortcuts" in what is usually a very lengthy, very costly process.
If one can pass four comps in maths, one has established PhD level knowlege.
The oral defense of the thesis establishes ability.
And, in more than one instance, the thesis itself has been handed in on the back of a napkin.
Having said all this, the number of folks that have actually gotten PhD's this way wouldn't fill a volkswagon.