Never heard of any voluntary holdback on transborder operations by AA as a result of the changes. If anything, they have taken a more aggressive stance, increasing their flights/destination between Canada-U.S. as equipment permits. Thus weekend specials would not be unusual.

AA weekend web fares are upgradable according to my own experience on YYC-DFW route last year [with Cdn stickers], as well as from postings on AA forums. Not sure of upgrade fare policy for AA Gold, however, but Platinum and ExecPlat are from any fare.

Although AA should accept the old CP stickers, you'd better confirm this with all the changes going on. They may not be under obligation to accept them on the old terms, and have already adjusted this year's upgrades to reflect CP's new eligible fare categories. This is definitely the case for the new CP stickers, which would not be useable on a weekend special fare.

[And remember upgrades on AA are in 500-mile increments, with the NAmerican system-wide CP stickers valued at just 1,000-miles.]