Quite a dodgy set-up... But as I always proclaim, there are 2-sides to a story, and the buyer was offered some compensation in the terms of 5 months free on a year extension, which was declined.
If the seller's response is true to the fact that the buyer got a substantial discount on purchasing the new car, then this leads back to the common question any consumer should ask, is the deal too good to be true. Then dig further and only go ahead with the deal if you are 100% satisfied.
Like the above article, shows how BMW does not support the customer, there are other stories I have heard where BMW has assisted customers out of goodwill even after the Motor Plan has expired. So I guess there is some good and some bad in every company, and some people will rave about the service, and others will complain, depends on each individual's experience.
I do sympathise with the buyer, however, according to the article, the buyer did receive a great deal on the car as well.