If a party identifies specific evidence that, if credited by the Worker’s Compensation Law Judge, would likely result in rejection of the witness’s medical opinion, cross-examination shall be granted. If a party fails to timely request cross-examination or to identify specific evidence that would likely result in rejection of the witness’s medical opinion, cross-examination shall be denied. Where the party has produced a medical opinion that contains a viable difference from or is contrary to the witness’s medical opinion with respect to the particular issue to be determined, the party shall presumptively be entitled to cross-examination.