The usual trick with any BA sale where you are looking for extra Tier Points is to check the American Airlines web site.
For example, BA is doing a fairly good deal from London Gatwick to Orland for most of 2014 (book by 28 Jan): (£1490)
This would typically earn 280 Tier Points with BA if you use their flights.
However, if you check the AA site you can earn an extra 120 Tier Points, and experience the new AA 777-300 if you choose your flights carefully:
AA is using a 777-300 to Miami.
In addition you can use the LCY-JFK (via Shannon) service which would earn 270 each way to Orlando:
A more extreme example is for flights to Sao Paulo in Brazil where the BA sale is £2601 for 280 Tier Points:
On the AA site you can book, via the USA for 560 Tier Points and a saving of £527, and two flights on the AA 777W!
So the moral is that if you are after Tier Points, check AA before you book on BA!