Are there no AY codeshares with P.E. outside the transatlantic and transiberian cartels?

AY already uses T for discount P.E. on transatlantic routes. I don't know what other codes are used, but from the codeshare earning table, I can guess they are P, E and W.

With that said, I am not sure why they need to reassign R, but it is true that they officially already use all letters except E (which I guess is for internal fares). U and X are for awards, F is for upgrades and all other 22 Latin letters else is assigned in earning tables.

Campaign W will probably be replaced by regular discount economy codes and a different fare basis. Wasn't the zero already used for that purpose? One less fare code for discount enomy, and two (out of four) for semi-flexible economy leaving only K and M there.