I doubt the anti-mob really believe a bridge is necessary (bar potentially improving access to Parkway for local residents). It simply serves as the biggest stick with which they can beat the club and scupper the plan. Should OCC back down, they will certainly try to use it as the basis of gaining further delays through claims that the Cabinet must meet to agree a fundamental change in the conditions under which they will agree to provide the land/potential for a Judicial Review.
Delays, leading to a loss of patience from our owners, are their best hope of ending this.