CrossOver allows you to add new drives and UNC paths to be used by Windows applications. Adding a new drive letter for a fixed device or changing a volume label is documented at the following location:
If you need to be able to access a UNC path in an application you can add an entry for the paths to your CrossOver configuration. Please note that browsing and dynamically adding UNC paths are not supported at this time.
Windows shares or UNC paths can be mapped into the ~/.cxoffice/bottlename/dosdevices/unc/ directory so anything trying to access \\myserver\share\file will look in ~/.wine/dosdevices/unc/myserver/share/file. For example, if you used Samba to mount \\myserver\share on /mnt/smb/myserver/share then you can do
Now any windows application trying to read \\myserver\share\file should be able to access it assuming there is no problem with file locks not being properly passed to the server. If you run in to problems, please file a support ticket.