Would you use a multiple wire ciruit (three circuits run together with ballast connected to alternating phase with a 3 pole circuit breaker) for fluorescent lighting instead of a one phase circuit? A specific situation would be rows of strip lights in a store. (At 277V) one circuit would serve two rows. A three phase circuit would serve 6 or so rows. If the multi wire circuit were used, should the neutral be oversized because of possible harmonics due to the elecronic ballast?
Basically a design issue, based on your input. Downside may be IF you have a fault...3 circuits 'trip' as opposed to one. Harmonics, with today's ballasts should be a non-issue. See Scott35's harmonics comments within another thread here.
The last lights I installed had a caution notice printed inside them addressing this very issue - that you need to be wary of harmonics issues.
IMO, there is merit to oversizing the neutral, at least through the first row of lights.
This does complicate your installation technique. The insulation-piercing connectors are designed for use with #12 wires. The same limitation arises with Wagos. Nor am I very happy connecting tiny ballast wires to a #10 with a wire nut.
Another possibility is to run a separate neutral to each set of lights, joining these smaller wires to a #10 at the start of the row. This would allow for the use of 'easier' connectors.
I have planned a few European commercial lighting systems, and we'd always run 3-phase circuits to feed the lights, but the ballast manufacturers (we mostly specified Osram) gave out leaflets with strict tables telling us how many fixtures we could connect to any given circuit, a number considerably lower than it would be expected were the lights resistive loads.