It's highly debated (I think), because, like letters of recommendation, the call can help (or hurt, or nothing) depending on who the two people are. Since this kind of equation is impossible to solve (i.e. does your attending know the PD? worked with the PD? Done admissions work with the PD? Is she liked by the PD?), you are likely spending energy on something that will be of uncertain plus/minus.
I have recently gotten 2 phone calls about an applicant from heavy-hitters in my Department. Without going into the details, these calls are *not* helping the applicant, even though I'm sure he was thrilled to get such big "names" to call on his behalf.