The comptroller of the treasury, in its discretion, may investigate an allegation of a felony that is classified as Class B or higher involving private funds if:
(1) The investigation is requested by the attorney general and reporter or the district attorney general of a judicial district;
(2) The investigation is in conjunction with an open investigation by the Tennessee bureau of investigation; and
(3) The comptroller of the treasury deems an investigation to be in the public interest.