The board of trustees shall contract with at least one (1) but no more than three (3) physicians who are not eligible to participate in the retirement system to serve as medical advisors. Notwithstanding this section or any other law to the contrary, the board of trustees is authorized to contract with one (1) or more companies or organizations for all or any part of the services necessary or desirable for the management and operation of the disability retirement program authorized in chapter 36, part 5 of this title, including medical advisory services. Any company or organization engaged to provide the medical advisory services shall be deemed a medical advisor for purposes of this part and for purposes of chapter 36, part 5 of this title.