(a) The trustees shall adopt an investment policy authorizing how assets in the trust may be invested. The policy shall not authorize assets in the trust to be invested in any instrument, obligation, security, or property that would not constitute a legal investment for assets of the Tennessee consolidated retirement system. The state treasurer shall be responsible for the investment and reinvestment of trust funds in accordance with the policies and guidelines established by the trustees.

(b) The funds transferred or deposited into the trust may be commingled with, co-invested with, and invested or reinvested with other assets transferred or deposited into the trust. All or a portion of the trust may be invested, reinvested, and co-invested with other funds, not a part of the trust, which are held by the state treasurer, including, but not limited to, assets of the Tennessee consolidated retirement system and the state pooled investment fund established pursuant to part 6 of this chapter. The assets of the trust may also be co-invested in a group trust in accordance with § 8-37-104(f).

(c) The trust fund shall consist of the following individual separate stabilization reserve trust accounts for the purpose of accounting for the employer contributions made to the trust on account of:

(1) State employees participating in the Hybrid Retirement Plan for State Employees and Teachers, compiled in title 8, chapter 36, part 9; and

(2) Teachers participating in the Hybrid Retirement Plan for State Employees and Teachers.

(d) In addition, the trust fund shall consist of individual separate stabilization reserve trust accounts established in the name of each political subdivision participating in the Hybrid Retirement Plan for State Employees and Teachers for the purpose of accounting for the employer contributions made to the trust by the political subdivision on account of its employees.

(e) The state treasurer shall assess a charge to the trust, in an amount to be determined by the treasurer, to meet the administrative and investment expenses of the treasury department in providing services under this part.