When it comes to cdo.dll you can copy it from Exchange to the BES. This only needs to be done if the BES version is lower than Exchage. Here is the process to follow:
1. Unregister all versions of cdo.dll on the BES - Just open a command prompt and navigate to the directory with cdo.dll. Run regsvr32 cdo.dl -u to unregister
2. Once all are unregistered, delete them
3. Copy the cdo.dll from Exchange to BES in the system32 folder and register it. Same as above but use regsvr32 cdo.dll to register it
4. Restart the Dispatcher Service
Are people experiencing Calendar issues? You said that you moved the database, so why are you moving users? If you moved the database then the users moved with it. What exactly have you done so far?