This is an easier way of addressing the non-collection of xbag charges.
If BA (or anyone) announces that they're going to apply the current rules strictly, it'll get no media attention and they'll have a shambles (more of a shambles?) at check-in, with howls of "But on my last flight..."
This way, they get loads of attention and if they promote the benefits effectively (which I haven't seen so far, actually), most people will see that they're not being disadvantaged.
Fargoo
What proportion of Economy pax currently check in more than 1 bag?
What proportion of Economy pax are currently charged excess baggage?
They're going to have to manage the issue of what to do with the 5 (or whatever) kg that needs to be removed from the overweight piece to bring it down to 23k.
You'll probably be able to buy standardised cardboard boxes or something. (Not that BA appears to have thought of that yet..)
Jewitts
If you're through-checked, the US/Canada rules should apply.