So here's a little help:

Fare Basis Codes are the letters/number before the "/" on the ticket. For example BBF/M2C234

Fares:

• Y26 is the only true full fare basis code. These always are UG'd into the P bucket (FC) at time of ticketing based on availability, if booked on nwa.com and a NWA Elite. If not booked on nwa.com you will be upgraded once a eticket is generated and the EUA sweeps.
• There are many other Y fare basis codes (aka Y-up) that indeed get you up front at time of ticketing, also into the P bucket. Most Y fares are indeed Y-Up fares.
• There are select Y fares, that are considered discounted and will not qualify as a Y-up fare, you will get processed in the normal EUA process and will move you into the R bucket. There are posts every few months from people complaining about these hidden non "y-up" fares.
• There are select B fare basis codes (BBF and B2P for example) that are considered B-up fares and will book you into P/First.
• There are B fares that do not get you into P, and you will be upgraded at the normal EUA 5-3-1 window into R.
• The same for M as B, though most M's are NOT M-up fares (in fact, in over 400 segments, I've yet to have an M-up)

Time of Ticket Upgrade Process:

• If you book on nwa.com and you have a Y-up, B-up, or M-up, you should be upgraded automatically at time of ticketing.
• If you book through a travel agent or third party, once the eticket is generated on the itinerary, EUA sweeps will move you into P, usually within 2-4 hours.
• It appears that if you are a CO elite, regardless of where you book, if you are on NW metal with 012 stock, you must call for your Y-up, B-up, or M-up fares.