In my own experience, if the trust is there that's exactly what happens. When there are disagreements, both parties can at least start with the assumption that the other person probably knows what they're talking about.
On an old project of mine, my friend said to me "I don't know why you think that'll work, and I don't agree at all... but somehow you seem to always be right about these things"
I guess it's pretty silly to start a big project with people you don't trust though.
