Either party may 'by-pass' the agreement before the actual execution of the plan.It is always advisable to continue a sort of "negotiation " with other party (whom we refer as plan B). It is not necessary to have a direct communication which could be done by our subordinates.
Ultimately, our priority is simply defined i.e. the entire process is meant for self interest . No matter with whom our 'deal' is completed. As long as we do transaction safely.