Sorry, but I came up short.
First, I confirmed that Line Port disconnect tone detection was working (with the local France disconnect tone).
I synthesized about 10 seconds of Spain disconnect tone and recorded it as a greeting on GV voicemail.
I repeatedly called the GV number, trying various values of DisconnectTonePattern; none worked.
I believe that either:
1. The OBi is not designed to detect an irregular disconnect tone pattern.
2. It can detect the pattern, but I don't know the correct syntax. Unfortunately, it's not documented and the default is the only example given.
3. It should be able to detect the pattern, but there is a bug.
IMO, you should contact OBi support and point them to this thread.