I've only met one person that did the Holman pathway and although at a prestigious program for fellowship this person seemed much weaker than the other fellows clinically. Most places don't seem to offer it outright, but might if you ask. I think it kind of died a slow death.
Many programs have their own version of it - e.g. UCSD has two research spots where you do a whole year of research after your intenship but before doing a 4-year radiology residency. I liked the place but personally I couldn't take another year off finishing training.