Seat Selection on codeshare
 

I am planning to book a YVR-AKL via LAX or SFO on the AC website.
All flights are in Y booked into "L" class. This class earns 100% status miles if I am correct.
Since the SFO/LAX-AKL flights are on NZ with AC flight number will I be able to make a seat selection during the online booking process?
It isn't a problem to do a seat selection if booked on the NZ website, however when booking on the NZ website it doesn't give fares that allow status miles accrual in Y.

Unikely. The AC engine can only book seats on AC metal, so you will have to call NZ once the res has been made to select seats on NZ metal if these show with NZ flight numbers. If shown as AC flight numbers, then call AC first.

Thank you SH. I have decided to book flights seperately YVR- SFO/LAX on AC website and SFO/LAX - AKL on NZ website, it is almost the same fare but this way I'll be sure to have everything in order and I get the best of both worlds:) .
On the AC website fare class "L" is listed for the codeshare which should earn miles however on the NZ website "L" booking class doesn't. I know different airlines have different booking classes, just don't want to have any surprises after such a long trip.

AC's L class most likely translates into S class on NZ, which earns zero mileage: "Air New Zealand flights in booking classes G, K, L and S are not eligible":

[KVS Availability Tool 2.8.1/Platinum - Sabre: Fares/ZUJ/SG-USD]

Ah, I was afraid of that. Eventhough according to the AC AP website L accrues miles I was worried that it might get mixed up and if the Boarding Pass would only show the NZ flight number there is a good chance for no mileage.
As mentioned in my previous post I will book now seperately as the NZ US website states very clearly which fares earn *A status miles and which ones don't. Let's hope by the time we get the Nonstop to AKL from YVR the Canadian website will be set up similarly.
Thank you KVS really appreciate it.

Don't forget the fine print: "For Air Canada code-share flights operated by another Star Alliance airline, refer to the Aeroplan Miles section of the carrier operating the flight."

Just be aware that you're connecting, but by doing so you your tickets and baggage are not: You will be responsible to have enough time to check-in at the connection point which also means clearing security again too. And, if you check any bags, you need to go down to the arrival bag belt first to retrieve your bag(s) before going upstairs to check-in for the connection. A pity: In LAX, AC & NZ are in the same wing, and at SFO, you would have been able to take the STAR Alliance shuttle from the AC gate area to the International gate area, all post-security.