Ah, I was thinking of the Debian package for hibernate, that has custom scripts for unmounting selected file systems, from the help text:

  "If you have network shares or external devices that should be unmounted before suspending, list them here."
  "Unmounts any filesystems of the given types. This is most useful for network filesystems such as smbfs and nfs."

And afaik it is perfectly possible to add ntfs mounts to that list - but I don't think any program with open files on that mount would handle it gracefully (I belive the script will figure out which processes (if any) have open files and kill them prior to hibernation).