I'm still struggling to get a response from British Airways, but I see this now under the "Flying with our Partners" section. Seems as of the 11th of January you now earn tier points on WTP flying IB.
But note the tier point calculator hasn't been updated to reflect this.
PS - I see now the text about this being for Iberia wasn't part of the screen shot but you can see it here:
https://www.britishairways.com/en-gb...-avios/flights