There is a chance, but you need some small effort to grab it it all (and some small knowledge of the registry and how to extract things)...
As said before, msgplus does not store your contacts emailaddresses unencrypted, but the .NET Messenger service does... Go to the registry:
HKEY_CURRENT_USER\Software\Microsoft\MessengerService\ListCacheU\.NET Messenger Service\
In there, and with some luck, you'll find a cached listing of the Allow list, Block list, Contact list and Reverse list....*
The lists are from the user defined in
IdentityName.
So, there you'll find entries like
Allow12. This is the 12th item in the allow list. The value is not ASCII but UNICODE. So there, with some luck, you can find all your contacts (provided that the value of
IdentityName is your email used for MSN Messenger AND that this cache is up to date)
* Allow list: people who can see your status
Block list: people which you have blocked
Contact list: the contact list
Reverse list: people who have added you to their list
more on this:
http://www.msnfanatic.com/index.php?module=announ...1&ANN_user_op=view
/ 
