If I did my math correctly, you are in trouble either way.
If you are supplying a 1200 main breaker, your total conductor ampacity must be at least 1200 amps.
Parallel 3/0 (225 x 2 x .8) in 3 conduits comes up to 1080 amps
In direct answer to your question, the neutral being a ccc depends on 310.15(B)(4) and if a majority of your load is linear or non-linear. We would need to know a little more about the load to determine. (Normally the neutral does not count on services)
(jumper answered that part as i was typing, sorry)
At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.