I just hit this issue as well. No mention in the fare rules that Business Saver isn't eligible for the chauffeur. Phoned up the help line and the guy said because I booked a "promotional fare" it's not eligible. I asked what promotional meant and he said "cheaper". After pushing he admitted that actually it's all Business Saver fares that are affected. I pointed out that if that was the case then they should just state that on the web site but all we could do was apologise for the inconvenience.
This is clearly Etihad just hiding the fact that they've withdrawn the service. How hard is it to state the restriction in the fare rules?