On a 3 phase panel - if 2 circuits share a neutral - do you have to use a 2 pole breaker so that if one trips they both trip?

14-010. It depends on whether the circuit feeds lights or plugs.

It isn't a trip issue, though. We can still use fuses as long as we include a disconnect that meets the requirements of 14-010(b).

It is for receptacles. Can you use 15 amp single pole breakers if the neutrals are being shared to more than one circuit?

the trade practice for three phase 4 wire circuits feeding 120/347 volts loads is single pole breakers. I could see good justification for a three pole breaker to ensure a circuit is completely disconnected included any current on a shared neutral but I dont think any code rule requires it. If the receptacle/load is using more than one phase then you need to use 2 or 3 pole breaker.

and before a bunch of posts come about the implications of common breaker handle for single phase loads, I can see some change in installation practice that will reflect the issue of current on shared neutral - such separate neutrals etc