TXL is a direct replacement of Lufthansa's LCY-TXL service, so Lufthansa probably wants to keep its product in the market.
MXP is part of Lufthansa Italia's massive build up in Italy, centered around the new MXP hub. It certainly does not make sense to dilute a recently established brand ("Lufthansa Italia") by adding bmi services. The target is mainly traffic originating in Italy, whereas bmi's brand recognition is restricted to the UK end.
Anyone done the maths by now? If I have mine right, 13 slot pairs are freed up by the reductions, whereas 10 are needed for MXP/TXL/KBP. Where does the balance go to?