Does this 3way loop control the fixtures in question? If so I say it is OK.
I wouldn't allow conductors from another circuit.
As Roger pointed out 410.31 and 410.32 are the requirements
If the fixture is listed as a raceway (410.31) which most fluorescent strips are you may treat it as just another raceway.
You want to run a 480 volt 100 amp 3 phase feeder through raceway listed fixtures you may.
If the fixture is not listed as a raceway then we have to follow 410.32.
410.32 Wiring Supplying Luminaires (Fixtures) Connected Together.
Luminaires (fixtures) designed for end-to-end connection to form a continuous assembly, or luminaires (fixtures) connected together by recognized wiring methods, shall be permitted to contain the conductors of a 2-wire branch circuit, or one multiwire branch circuit, supplying the connected luminaires (fixtures) and need not be listed as a raceway. One additional 2-wire branch circuit separately supplying one or more of the connected luminaires (fixtures) shall also be permitted.
The travelers are
part of the lighting circuit supplying the fixture.