The rules were simplified for 2018. Ticketing carrier was still a factor in 2017.
For most of 2017, yes. But I was surprised to see VA flights on a mixed DL 006 issued ticket earn based on mileage in Oct/Nov 2017. Because this was DL ticketed I'd been expecting to earn based on DL $ rules.
DCA-LAX-BNE earned $ based with DL flight numbers (LAX-BNE was VA operated).
BNE-AKL/CHC-SYD-LAX earned miles based as all flights had VA flight numbers and were VA operated (the reason I had a 6 hour layover at BNE -- VA and NZ code share a lot of OZ-NZ flights and the first connection to AKL was NZ operated, so would not have earned miles. And I think that CHC-SYD was operated by VA on some days and NZ on others).
LAX-DCA earned based on DL flight number and operations.
FWIW
LAX-BNE 7,161 actual miles (earnings based on $s) 10,742 MQMs, $1317 MQDs, 14,487 flight miles (base+bonus)
SYD-LAX 7,489 actual miles (earnings based on distance) 11,231 MQMs, $2995 MQDs, 23,958 flight miles (base+bonus)
As much as I tried, I couldn't get the LAX-BNE flight to show up with a VA flight number.
As I recall, the whole ticket -- DCA-AKL/CHC-DCA in business cost about $4500 including taxes and fees. I earned $6072 MQDs for the whole trip including the DCA-LAX-DCA flights.
If you are on an expensive ticket then it may not work out, but if you find relatively cheap business class tickets, booking with partners can be great.