Irrespective of your personal specific situation, if the contract says based in city B and now it’s going to be somewhere else, then that requires either them renegotiating the contract with you, or terminating the contract and negotiating a new one with you. Either way the bond is linked to contract stating city B as your base.
Without being an expert I’m guessing that argument would hold in most courts as well. Question in these cases is always - How far are you willing to take things?