REM said:
Is there a code violation for using non-metallic raceways in Fire Alarm Circuits ?
It all depends. Where do you live? Many jurisdictions have special wiring rules for fire alarms systems.
Here, all FA wiring has to be in metal raceway and/or MC cable. If you live in or near Chicago you will be installing all of your wiring, including fire alarm systems, in metal raceways like EMT and RMC. Las Vegas requires a metal raceway system for fire alarm. Some states have different rules from town to town and city to city, like Massachusetts. Those are just a few examples but the bottom line is that you need to check your local codes.
There is no rule in the NEC or NFPA 72 forbidding it, however.
Edit to add more examples of local rules.