I should point out, though, that the whole "applying to TYs in areas I am applying in rads" gambit is not as easy as it sounds, for several reasons:
#1 Even if TY/prelim and Rads program in question are in the same city, it is often more of a headache than it sounds like. Take Boston as an example. Brockton, Caritas, Shattuck are all at least 20 minutes outside of Boston, so unless you want to deal with a big commute from the city every day for a year, you'll probably have to move your crap twice anyway. Or Flushing, NYHQ, MSKCC in NYC. You want to commute from Manhattan to Flushing every day? Or, if you get MSKCC's subsidized housing if they still offer it on the Upper East Side, what if you match Columbia for Rads? Getting from the Upper East Side to 168th on the Upper West Side is actually kind of a bitch. And on and on. Unless you are damn lucky with geography and two reasonably closely spaced programs (Let's say Albert Einstein TY / Penn Rads, MSKCC TY / Cornell), you're going to have to deal with either a ****ty commute one year or a double move. The best bet to avoid moving twice or commuter hell is to stay at your home program, go for the few "integrated" programs with built-in prelims (e.g. Emory), or suck it up and go to the generally brutal med or surg prelims at the same academic institutions you are targetting for rads. Hopefully you are fortunate enough to have some good options.
#2 There are usually preset handful of interview dates, and whether the interview dates of the TY/prelim and rads programs in the same geographic area line up is entirely up to chance. And by the time you get both interviews, you may have already scheduled another interview elsewhere, because the season is generally so tightly packed. Again, if you suck it up and go for the brutal med/surg prelims at the academic institutions where you are targetting rads, then there is generally more flexibility to coordinate prelim and rads interviews on the same day or consecutive days, but even then don't count on it.
Long story short, it sounds nice but it's going to be a nightmare. Good luck.