Here are the OnePass partner mileage accrual rules from the OnePass website...
Northwest:All Northwest, Northwest Airlink* and Northwest
flights operated by KLM
*Includes Mesaba and Express One Airlines
American Eagle:Continental codeshare flights connecting over LAX
from a Continental operated flight or Continental
codeshare ticketed passenger flying on a Virgin
Atlantic operated flight to or from Bakersfield (BFL),
Fresno (FAT), Monterey (MRY), Santa Barbara
(SBA), San Luis Obispo (SBP), San Diego (SAN) or
Palm Springs (PSP).
So from looking at these rules I would have to say no, that you techinically could not earn miles on the LAX-MRY segment if it was ticketed with an NW code. The only way you could get miles if that same flight was coded CO and you arrived in LAX on a CO flight (no codeshares except VS).
So unless you are deadset on flying Northwest or Northwest is cheaper than Continental you won't get miles, unless they end up giving them to you by accident.
Stop drop and roll will not save you in hell. --- seen on a church marque in rural Virginia