My travel has all been to RJ-served little towns in the Midwest or the South. I'm based in SFO So I always start with CO SFO-IAH or NW SFO-DTW/MSP

SFO-IAH: no, never, 0%, not on a Sunday afternoon or Monday afternoon. Zip.
IAH-SFO: 100% Always battlefield, always clears, at least on the 9.10pm flight

Whereas on NW I was getting upgrade to DTW as a Silver on occasion, as a Plat its almost certain.