Brian,
Remote-Party-ID is a long-obsolete draft that never became an RFC; why are you still using it?
Anyway, if you know the 'privacy' header parameter will always be there, you can do this, assuming is_present_hf("Remote-Party-ID"), of course.
$var(x) = $(hdr(Remote-Party-ID){s.select,1,>});
xlog("L_INFO", "Remote Party ID privacy value: $(var(x){param.value,privacy})\n");