Well, like I mentioned, we have had no problems with the BB to Outlook wireless calendar sync. Just today someone contacted me and I noticed the problem also. I had the mail team send me the cdo.dll they were using and I registered it on the BES. Wireless entries from the BB to Outlook are now working again.
So far I haven't seen the duplicate calendar entries appear either. Those would happen sporadically on BB entries.
Update - well, now the BB entries aren't syncing to Outlook again! Still no duplicate entries though.