I've been disrupted on a CBR-NRT flight tonight. I was meant to be in the air right now on QF21 out of SYD, but crosswind and runway issues in SYD caused delays to my flight out of CBR which would have lead to missing the connection.

QF then rerouted me onto CX via MEL and HKG.

It's a W (premium economy) ticket. QF had op upped me to J on QF21 some time today, though I lost that when I was rerouted. They tried to get me into W on the CX flights, but ended up grabbing what they could.

I was checked in and issued new boarding passes right as the CBR-MEL flight started boarding.

When I got to the CX lounge, I found that CX had given me an op up on MEL-HKG.
I've had this routing for all of 2 hours and no CX status (though OW Emerald via QF) BN 63.
Seams odd that CX would upgrade me that quickly instead of someone with CX status.
Would having a DONE3 issues by CX in the system (easily referenced by QFF number) have helped?

You are asking a pretty complicated question and one you likely will never know the true answer to.

But I would guess it's simply plain luck of the draw and you were the next up for an op-up. What's your status with QF? Being in oneworld your status with QF gives you some level of op-up priority with CX. See CX's order of op-up priority in the FAQ here. That list is not officially confirmed so obviously YMMV.

I'm 6th on that list.

I'm a CX Gold (4th on the list) and I get lots of long haul upgrades without really trying very hard. So it's no surprise that a QF Emerald would catch one every now and then.

63 is actually a pretty decent BN considering there are a few hundred on your flight. Assuming you fly in J please take a walk through the W & Y cabins to see if they are full enough to cause you to be op-upped. If they have lots of empty seats, then it must be a computer glitch or an artifact of your DONE3.

As a matter of fact, CX MEL route is by no means a diamond-rich route, and I don't believe it has many golds either, which would then bring you to the top of the list.

Ps. Wen you got your CX BP was it in Y+?

Compare to SYD, MEL do have less DMs

I was issued passes by QF for all 3 flights (CBR-MEL-HKG-NRT) right as the MEL flight started boarding. CX178 was a Y+ seat row 33ish. When I got to the CX lounge, I was reissued CX passes with row 16.

QF hooked you up

You are right, I used to fly the MEL route a lot and it seemed to me that most of the MPC members are either GR or SL, it didn't look like there were many golds on any of the flights, certainly not diamonds