(a) If the employee who has completed rehabilitation previously worked in an employment position subject to random or arbitrary testing under an employer's written policy, the employer may refuse to allow the employee to return to the previous job if the employer believes that the employee may pose an unreasonable safety hazard because of the nature of the position a position that would create an unreasonable threat to the health and safety of the public, the employee or coworkers if the employee were under the influence of a substance of abuse, the employer may refuse to allow the employee to return to the previous job if the employer believes that the employee might pose an unreasonable safety hazard because of the nature of the position. The employer shall attempt to find suitable work for the employee immediately after refusing the employee's return to the previous position. No reduction may be made in the employee's previous benefits or rate of pay while awaiting reassignment to work or while working in a position other than the previous job. The employee shall must be reinstated to the previous position or to another position with an equivalent rate of pay and benefits and with no loss of seniority after an evaluation conducted by or arranged through the rehabilitation or treatment provider concludes that the unreasonable safety hazard has abated, or in any event within 6 months after returning to work in any capacity with the employer unless the employee has received a subsequent confirmed positive result within that time from a test administered under this subchapter or unless