Originally Posted by
MrDooog
Where did the OP say they were looking at booking in J?
I think that it is implied by OP since OP asks about how it may impact TP earning. I doubt that a TP run in Y would make much sense (particularly when looking at cheap tickets).
[MENTION=872985]babrln[/MENTION]: You can feed the routing information into the BAEC calculator and see the difference in earning Avios/TP. I've booked for similar reasons AA flights on BA codeshare numbers. The ticket on AA flight numbers was twice as expensive.