Best way to do it is to remove the clamp bolts; insert something like a 3mm T handle allen tool into the brake pivot and a 4mm allen into the hole where the clamp bolt was-not across into the threaded bit, and then very gently spread the alloy clamp to pass over the carbon; put a bit of tape around the carbon to prevent scratches and get someone else to hold the fork steady. I have done this many times without wrecking the clamps-they take a bit of squeezing and realigning, or damaging the carbon. It isnt easy trying to pass the over the dropouts btw.
Hope that helps