You cant expect the iphone or even every single phone in the world to be compatible with all bluetooth systems.
It's just the way it is. For what its worth my iPhone 4 works perfectly
with a brand new Ford truck ( my friends not sure the model) Sync system
we play music, take phone calls and works without a hitch.
considering the underlining technology behind ford sync Apple does not have an excuse. It basically means Apple is refusing to play nice with MS. MS provides the standards Apple is the one failing to address the issue.