It works. Obviously if you get the opportunity to have a discussion with the prospect upon presenting the bid, even better.
I have seen this to work especially well with both maintenance and design.
Design/build has so many variables to it and if the contractor does not do a sufficient job explaining the difference between using product A versus product B (quality, warranty, maturity, etc...) then they are leaving it up to the client to decipher these things.
Never a good idea.