I believe the big consortium buy for PW was down to the fact of available machines in a short time since the TM ones appear to have a longer waiting list, also TM want ultra clean water for their engine rinses which used to be daily but PW are happy with tapwater things like this had a bearing as well.
Well this is how I understand it.
All most all of Germany's Air Ambulance use the PW. The one in Berlin (I think) even has airfilters.