[Dovecot] shared folder

The dovecot wiki says:

The only way to implement shared folders with Dovecot 0.99.x is to create a "shared userid" which all of the users log in to read mail.

Does this mean that folders owned by that shared uid can be *simultaneously* manipulated by multiple users logged in to that shared uid? This doesnt seem to be the case on my dovecot-0.99.11-4.EL4 system, and before investigating further I just wanted to check whether it should be possible or not.

Cheers, Terry.