A test: I gave one GMail account edit access to another GMail account (yes, you can do this) and started editing an e-mail, saved it as draft, and then went to the other account— the draft was there, but not only was there no autorefresh of the other's changes when i edited simultaneously, but it forked and created two drafts of the same e-mail.
Except where otherwise noted, content on this site is licensed under a Creative Commons Attribution 3.0 Unported License.