Since the ciphering algorithm A5/2 encryption is weaker (encryption security) compared to A5/1. Would there be any other reason for an operator to use the ciphering algorithm A5/2 only on their BSSAP end, but A5/1 on MSC PLMN?
… or perhaps there is another operator using A5/2, and therefore they are also using A5/2 in order to avoid intra PLMN HO failure ? 5change of ciphering during a HO is certainly a little bit complicated…)