So why did Angus Houston make his clear statement.
Dick, can I suggest that when Sir Angus referred to 'two almost identical air traffic management systems' he is simply referring to the technology bit. That is, TAAATS and ADATS - the consoles, radars and other sensors, radios and the software and network connectivity that ties it all together.
He was not, I believe, ever referring to the system of systems that make up an ATC service/ANSP such as HR, training, AIS, regulatory framework, technical wokforce etc.