Hello, very new to the AC bid upgrade program as I don't (if ever?) fly AC on AC ticket.

I have a flight from YYC-YYZ on Oct 11 (red eye) on A330-3 (continuing later to DTW on same ticket). It is offering me a bid for business as low as $275, and buy now for $480. There are 12 unassigned seats per EF (don't have premium so can only see seat map) but they just added the buy now option since last Thursday. the 480 is a bit expensive for a roughly 3h50m flight, but since it is a redeye and I have plans early in the morning after I land it is definitely worth the 2-300 range.

Anyway, the question I have is does the bid range ever move around? That is now it is 275-585, will that range change? Will the buy now price change at all between now and T-48 or so if seats get bought up or not? Not sure what to expect as this is my first experience.

Also, as a side note, I assume my Star Alliance Gold via United allows me to access to the Maple Leaf lounge since I am international ticket?