Hi,
Did you have the ignore.conf file set up before FMOD was checked-in or was it added after?
If a file is already under version control the ignore.conf file won’t work.
An option is deleting the file in Plastic SCM and checking in the deletion. This will stop the file from being tracked and remove it from your repo. Run Unity again, which will create a new .log file on your disk but it should now be ignored. Once it has been successfully ignored have all your collaborators update their workspaces with the file removed.
Hope this helps.