The older child was breast fed from birth to around eight months. This child is developing normally. Mother is well, as is her renal transplant function. Both children are entirely well. The mother is now concerned about the risks of feeding the second from the breast, but wishes to continue breast feeding.
Literature is sparse here too.
These are the only two articles of relevance I can find. Novartis has not been any further help - just warning against breast feeding, because of lack of evidence either way.