To be fair, the E200MMC's will be thrown on anything and everything. I don't think they really care about what routes get what nowadays and they just simply make sure each service is running regardless of the bus. Wouldn't surprise me, if they throw them on the X4, X12, X22 & 5 as they're brand new. The 63/64 & 65 will most likely still be mostly Pulsars and to be honest, all the Pulsars are capable of working for another 5 years. But Yeh, atm I think Arriva just need to focus on having every service running at the max efficiency.