Having been privvy to much primary sources of info within the EH101 International Project Team, DOR(SEA), Westlands and private conversations from many involved at the coal face I have to both disagree & agree with DM to some degree.
The RTM322 was specified a very, very long time before the Active Dipping Sonar was a requirement. The two are not linked. The original requirement was written at a time when "passive sonar was king" and the RN did not envisage the cab going to sea with an ADS. However it is true that the original requirement called for the provision of facilities for ADS at a later date if necessary. What the requirement did not say was that ADS had to be provided whilst retaining the need for an AUM that still allowed the 4 hours time on station. The RN still wanted all of that, & naively thought that what it was going to get, but it was impossible. Westlands provided a hydraulic feed & voltage & when the ADS was finally specified, the RN were surprised that the weight had grown!
And no matter what the gearbox design experience of Agusta & Westland was, it is a fact that the gearbox was an Agusta workshare item & that it was not able to handle the power that the RTMs could deliver, or the power that the alternative Westland designed gearbox was supposed to be able to handle.