What do you mean by physician scientist training pathway? The dirty little secret is that the PSTP really doesn't exist.
The American Board of Internal Medicine has a set research pathway (
http://www.abim.org/certification/policies/research-pathway-policies-requirements.aspx). The majority of academic residency programs will allow you to go through this pathway in which you do an PGY-1 and PGY-2 as a resident and then do a PGY-3 as a fellow ("short tracking") in exchange for doing an extra year of fellowship.
What programs advertise as the PSTP varies dramatically. The MSTP offers I received seemed to be really straightforward. It was my experience that most PSTP programs were not at all honest about what they offered. At the bare minimum, they offered the possibility of short tracking, but I think most academic programs would be amenable to you doing this even if they don't have a formal pathway. That being said, I interviewed at one place with a "research pathway" where pulmonary/critical care refused to accept short trackers and heme/onc strongly discouraged it. I had to probe to find this out.
Many "guaranteed" fellowship admission with lots of string attached (e.g you can't switch fellowships during residency, the guarantee can be revoked at any time, it only applies to certain subspecialty fellowships, etc). None of this was volunteered to me during interviewing. Some guarantee you funding for that extra year of research and some do not, and sometimes it depends on the fellowship you're in and can change from year to year depending on the funding of the fellowship and the whim of the director. Some even force you to do that extra year of research as a PGY-3. Some programs offer you an extra bonus as a fellow to deter moonlighting. Most do not.
So when you say you want a PSTP, what do you want out the program? That will help answer the question.