Yes, you will definitely get full AP miles - but you would have earned them also if your flight was booked using the OS Flight number, OS is a *A member.

I found the OS service nice on my last flight IAD-VIE in late March, although flying their "Grand Class" at that time. Their business class seat reclines pretty good, but unless you are sitting in the bulkhead row the fully reclined back of the seat in front of you may squeeze your feet if you put up your (for my taste way too short) footrest completely.