A SET OF PLANS THAT HAS 4- 3/0 CONDUCTORS WITH A #6 GROUND IN RMC. LENGTH IS > 10 FT AND IT SUPPLYS FOUR ATTACHED STRIP MALL UNITS. 200 AMP SERVICE AT EADCH UNIN IN RMC THAT WILL BE BURRIED. HE STATES THAT SINCE IT'S 3 PHASE IT DOESN'T HAVE TO BE DE-RATED.
If you are asking about adjusting the ampacity for more than 3 current carrying conductors in a raceway you need to look at 310.15(B)(4) for when a neutral conductor counts as a current carrying conductor in regards to the ampacity adjustments in 310.15(B)(2)(a).
Most likely the neutral will not count as a current carrying conductor.
if your using copper conductors, at least 75 degree rated, then chances are good that only the 3 hots count towards the derating max. If, however they are aluminum, and 60 degree rated, they will not come close enough to 200 A to use a 200A breaker.
Use the table mentioned above to find your answer.