Many local codes are more stringent than the NEC with regard to fire alarm wiring. In my area, all fire alarm wiring has to be in metal raceway and/or MC cable.
Only your local authority can answer this question.
Also consider what the system is being used for. If the system is being used for a Fire Suppression system in accordance with NFPA 2001 (2008 edition, and earlier), section 4.3 makes the following statements:
4.3.1.1 Detection, actuation, alarm, and control systems shall be installed, tested, and maintained in accordance with appropriate NFPA protective signaling systems standards. (See NFPA 70 and NFPA 72. In Canada refer to ULC S524-M91 and ULC S529-M87.)
4.3.1.3 Initiating and releasing circuits shall be installed in raceways. Other than as permitted in 4.3.1.3.1, alternating current (ac) and direct current (dc) wiring shall not be combined in a common conduit or raceway.
4.3.1.3.1 Ac and dc wiring shall be permitted to be combined in a common conduit or raceway where shielded and grounded.