Are they rebuilding all their indexes and then updating stats at 20%?
Or, perhaps, rebuilding all indexes where fragmentation is greater than 50%, reorganizing all indexes where fragmentation is greater than 20% and not updating any statistics at all?
Or, my personal favorite, autogrow in 1MB increments followed by a weekly shrink. OH YEAH! http://youtu.be/OG_6CopW9GQ”
Objectively point out where the maintenance plan does not line up with this link: http://technet.microsoft.com/en-us/magazine/2008.08.database.aspx?pr=blog
Let the data do the talking. If they still circular file your recommendations, then you have to do a risk assessment on whether it is worth having the DBAs hate you when you go over their heads.