Col,
If the C27 cannot be supplied or supported then it looks like we have to start again.
If the project documentation is written around a requirement there should be no need to start again; just look to the next best available option.
Of course, if BR71's assertion below is as true now as it was then, that would be another matter.
It is very easy to write a requirement in Canberra around whatever a particular lobbyist is peddling and thus scratch other competitors because they do not exactly equate. That was going on during my time in that place.