Answer:
No, the broker is not responsible for either the exit ramp not being built at that place or the client deciding to buy the property believing that a exit ramp was supposed to be built there.
The broker had the responsibility of telling the client that there was a chance that an exit ramp could be built there. If he hadn't done it, the client could have claimed misrepresentation in case the client wouldn't have purchased the property and the ramp had been effectively built there. He told her that the building of the exit ramp was proposed but it wasn't 100% sure.