Does NFPA 70 (NEC) 2008 allow you to use THHN wire instead of FPL on PLFA Fire Alarm systems?

A contractor gave me an NEC code reference to 760.130 saying this allows you to use THHN on Power Limited Fire Alarm Circuits so I looked it up and found that on the load side of the Power Limited Fire Alarm power source you can use wiring methods and materials in reference to 760.46 which addresses installation of non-power limited fire alarm circuits (high voltage) then there is a reference in 760.53 that states that multiconductor non-power limited fire alarm cables (high voltage) that meet the requirements of 760.176 shall be permited to be used on fire alarm circuits operating at 150 volts or less (which is POWER LIMITED)and shall be installed in accordance with 760.53 (A) (1), (A) (2) and (A) (3) so then we go to 760.176 and we find a chart that goes back and lists Multiconductor cables and their acceptable subsitutions which are CMP or FPLP or CMR or FPLR or CMG/Cm or FPL so the CMP, CMR and CMG/CM are commmucations wire and cables and the FPL, FPLR and FPLP are Fire Alarm Cables. FPL is general use, FPLR is riser wire able to hold it's own weight in a shaft and avoid the spread of fire up the wire and FPLP is plenum rated that meets or exceeds the other requirements and does not put off as much toxic fumes. Then you find more detailed information in 760.176(G) about the fire wire on page 70-632 so the reference for using NPLFA cables on PLFA is 760.53 as long as it meets the 760.176 but I still don't find THHN listed but apart from that I understand the comment about installing what was specified and on the case where the AHJ made them take it out the drawings clearly listed FPL, FPLR or FPLP cable and THHN was installed although I did not argue because it was for horn/strobes on that one and they would work just fine. The conduit they installed them in was EMT not ridged. It is difficult when you install a fire system with data transfer where you need the certain twists per foot (normally 12) and an engineer specifies THHN which does not meet manufacturer recomendations and ends up causing issues. Why would a contractor install THHN when FPL is less expensive and encased in a jacket already with 2 conductors and they pull it off separate spools? Just because they have it on the shelf? :-? Can you use THHN cable normally used for Non-Power limited circuits (high voltage) on Fire Alarm Systems which are Power Limited circuits (Low voltage)?