He has produced examples showing 3 mil traces that look very impressive.
Available information is coming via the "Homebrew_PCBs@yahoogroups.com" mailing list.
His method evolves a laser printer with a straight through print path (E260). He has modified the printer with a high(er) voltage image write cycle and tricks the printer's sensors as necessary.
Update: Mark has abandoned the high(er) voltage modification and said it was not necessary, see his updated documentation.He plans to document his method as he solidifies elements of the idea.
As someone mentioned on the mailing list; "Direct Laser Print to PCB" is the "holy grail" of the Homebrew PCB Toner Etch Resist Method. Hopefully it can be perfected.
This is going to be a very interesting project to watch.