As augmel says, the answer is no (sort of) and yes. In general, you can get up to 6 mos of credit for a non-IM program if you transfer into or re-match into an IM spot after doing part or all of another residency. Obviously, Path and Peds will give you no credit but Surgery and FM might get you 6 mos.
As for the Fast-track, yes, the ABIM Research Pathway is available for people interested in academic research careers. Calling it fast however is a misnomer. You do 2 years of IM (which of course speeds things up) but b/c you have to meet all those ABIM requirements in 2 years rather than 3, you end up w/ more call/inpt months each year than your colleagues (I have 9 this year while most of my co-interns have 6-8). The second issue is that the fellowship actually ends up making the whole process longer than a straight IM + Fellowship.
As an example, Hem/Onc requires 3 IM + 3 H/O for 6 years total. "Fast Track" requires 2 IM + 1.5 H/O clinical + 3 years research fellowship for a total of 6.5 years. Cards requires a full extra year if you do the research pathway.
So if you're looking for a quick way out, there really isn't one. But if you know you want a research and clinical career, the research pathway is a great way to go.