§40.149
No. The MRO is the only person authorized to change a verified test result (see §40.149(c)). The MRO can do so with respect to a verification decision he or she has made, in the circumstances described in §40.149.
An arbitrator is someone who derives his authority from the employer, or from a labor-management agreement. The arbitrator cannot exercise authority that the employer could not exercise on its own. The arbitrator could not overturn a decision of the MRO concerning a test verification any more than the employer could on its own.
This prohibition applies to substantive decisions the MRO makes about the merits of a test (e.g., with respect to whether there is a legitimate medical explanation for a positive, adulterated, or substituted test result or whether a medical condition precluded an individual from providing a sufficient specimen).
An arbitrator could determine that a test result should be cancelled because of a defect in the drug testing process involving the MRO (e.g., that the MRO failed to afford the employee the opportunity for a verification interview). But an arbitrator could not overturn the substantive judgment of the MRO about whether, for example, the information submitted by the employee constituted a legitimate medical explanation.