Okay, here is the way I understand it the priority list after speaking with CO and NW agents. Notice the subdivisions of fare class within each used as "tie-breakers" if there are 2 Platinums say vying for the same last seat.

CO Platinum
- Full Fare
- Economy
CO Gold
- Full Fare
- Economy
CO Silver
- Full Fare
- Economy

CO tried to tell me it was time sensitive and subject to EUA however when I asked the agents if I am Silver and book a ticket 21 days before a Gold could I get the upgrade before them and she said no. So supposedly within EUA there is another way of handling upgrades apart from the first-come, first-served basis it implies. The above list I think goes into effect when tickets are under airport control instead and are at the gate agent’s discretion as well.

NW agents were more friendly regarding upgrades and mentioned the following, if the flight is a NW flight number operated by CO, then yes I could upgrade with KLM RW if a seat is available. It is an unpublished benefit as KLM is a partner. However,
if the ticket is CO flight number and operated by CO, then NW can not access the reservation to put in the upgrade unless there is at least one NW segment in the itinerary.

Too confusing? Go on Jet Blue instead- satellite TV at each leather seat and brand new Airbus and no fuss about upgrades. It seems that what a lot of people in JFK area are starting to do.