It seems to make no difference to NW/KL which airline is carrying you. They will permit a mileage upgrade on Y,M, and B fares but, and this is the caveat, the bucket for these upgrades has always been in my experience, severely limited. This bucket is not transparent on the class availability tools, but if you check http://usr.v7.com/wpaa/ you will find out fairly sure which flights have award availability. This is reputed, according to the NW board gang, to track fairly closely with the upgradeables since it appears that X number of seats are held out for sale and Y number are permitted to be used with mileage in some way or other, whether upgrades or awards.
There is another source of information about NW awards which has been created just for the Asian market but I'm not sure how applicable it would be to US originating flights. You can find this one at
http://book2.nwa.com/jp/booking/asp/...ONID=846396066