I've cleared my inbox since then so don't have the confirmation details, so, no, I'm not sure if the outbound & inbound fare classes were the same. In hindsight, I would suspect not, but remember the ac.com site at one time explained various pricing options across the pond; there were two lower-class economy fares available (called Leisure & Tourist if I recall). These options didn't appear on this booking, and thus I couldn't ensure I avoided the fare that only credited partial miles.
At any rate, I do recall both Leisure & Tourist classes awarded full status on the international segments, but they never did stipulate what happens if you sit in partner (LH) metal.
It (explaining the fare class more clearly) was the focus on my survey response following my visit to the ac website today.