I can't speak to the splices, but you are correct in saying the ceiling grid should not be used for support of any cabling.
The NATIONAL ELECTRICAL CODE (NFPA 70)
-
300-11. Securing & Supporting
-
A) Raceways, cable assemblies, boxes, cabinets, and fittings shall be securely fastened in place. Support wires that do not provide secure support shall not be permitted as the sole support.
1) Wiring located above a fire-rated floor/ceiling or roof/ceiling assembly shall not be secured to, or supported by, the ceiling assembly, including the ceiling support wires. An independent means of secure support shall be provided.
2) Wiring located above a non-fire-rated floor/ ceiling or roof/ceiling assembly shall not be secured to, or supported by, the ceiling assembly, including the ceiling support wires. An independent means of secure support shall be provided. Cables and raceways shall not be permitted to be supported by ceiling grids.
Also, contrary to popular belief, fire alarm cables do not have to be red, only that they be readily identified. (NFPA 70:760.30)
In fact, here's some in BLUE.
This is from the standpoint of the NFPA Standards when referenced by state and local codes. If the state or local jurisdiction does not reference NFPA 70 (the National Electrical Code) or amends it, your mileage may vary.
Finally, some AHJs (Authorities Having Jurisdiction) may enforce local "customs" as if they were legislative codes when they are not.