The problem is that in cases of delay, cancellation, or other problems, airlines will put you on the flight you want but not to another destination as originally booked. This is not just AF (there is a thread on exactly this in the BA forum about a particular incident at the moment).

Of course, you can accept their rerouting, seek compensation for the delay and more than pay for your new train ticket (or a flight to OSL) with the money which will cost AF more, but sadly, reservation people won't deal with that so they won't care. Again, however, it is the same with other airlines in my experience (like you, over 200 flights/year).