Yes.

If you know the routes, goto www.seatcounter.com

Punch in the Orgin and Destination airports. Then under "preferred carrier" put "UA" in two boxes.

What will come up is the "buckets" for each fare class that are available on that particular flight.

Upgrades from Y to C show up as the NC fare bucket (aka I)

Upgrades from C to F show up as the NF fare bucket (aka X)

Upgrades from Y to F (two class) show up as the NF fare bucket (aka X)