All students should realize that it is not unheard of for program directors and other members of the selection committee to call faculty who have written letters of recommendation on your behalf. If your letter-writers have written you a strong letter of recommendation, you should not be concerned about the residency program calling them. You should, however, keep your letter-writers abreast of how things are going for you in the residency application process. That way, when and if, they are called, they will be informed about your progress in securing a residency and will speak about you enthusiastically. One of the biggest mistakes students make is not keeping their letter-writers informed of what's going on.
As for program directors calling one another to discuss their applicants, in my previous post, I mentioned that this does not happen often. I base this on discussions I have had with program directors of various specialties. Can I say that it never happens? No, I can't but for a minute let's consider what this would involve. Even in competitive specialties that have relatively fewer residency programs, for the program director to discuss your application with other PDs, he would have to know where you interviewed and then make calls or inquiries to all of those programs. Keep in mind that you are not their only applicant. So the PD would have to do this many times over. As someone who has been involved in the selection of residents, I know that it is an incredibly busy time of the year for program directors and members of the selection committee. Imagine the time it would take for these folks to do all of this checking up on you.
Having said this, I can still understand your concerns. If you remain concerned, instead of emailing or writing them to inform them that they are your #1 choice, why not use the words "highly rank". You can such language when communicating with multiple programs - then you don't have to be so concerned.
Good luck with everything,
Samir Desai
Assistant Professor of Medicine
Baylor College of Medicine