I'm not quite sure which flights are cancelled, and I'm also unsure whether you want First travel or First Tier Points. I am going to assume you booked this as a revenue ticket with BA codeshares on AA rather than AA prime flight numbers, or indeed a redemption. And that it's a BA plated 125 ticket.

If all the above assumptions apply then BA will need to rebook you. And they will in the first instance be looking for the same fare bucket on BA codeshare flights. You are free to persuade BA to put you into AA prime flights instead, and if they are two class you will get both AA First travel and First tier points; but if there is codeshare fare buckets available I think they'll try and get those for you, and you will be left in a similar position. Before calling it's best to do some research as to what is available, so you don't accept the first thing that they suggest. Having rebooked you once, they are unlikely to give you a second involuntary rebooking.

Feel free to clarify, as you can see it's a bit fiddly.