No, I don't think so. Not unless you are accustomed to typing your password directly into the terminal prompt. Kill buffers don't pass from one application to another and they don't all behave the same in every context, either.

(For example, if I type some stuff and then ^U to kill the password buffer at an SSH password prompt, typing ^Y after that seems to put the whole process in the background. Not sure what that's intended to do, but subsequent ^Y presses don't retrieve the password into the shell prompt...)