I take your point but the authority clients are political too, politics aren't restricted to central government.
My point was coming from the perspective of seeing those politics in "action".
To use rolling stock as an example, the procuring authority decides its about time for some new rolling stock. They look around the room and the only person there who's been involved in any rolling stock deals is Gary, and he's about to retire (i'm exaggerating, but the point is that they generally lack a team capable of such a project without pulling in significant resources/expertise) .
So, they go out to the market and pick up a set of advisers (technical, design, legal, finance, insurance etc) who do these sort of deals constantly. On fairly unique deals they'll also pick up a commercial lead with a track record in getting these things done.
So now you've got half a dozen guys from the authority who will "lead" the deal, supported and guided by their team of advisers.
First task...it will take a year or two to set up the competition. The contracts, the financials, any reference design, the procurement issues, and regulatory stuff.
So where do you start? Well the commercial lead will start with the last deal he did which didn't get successfully challenged, the lawyers will dig out a set of contracts which worked ok and are a good match, the finance guys will start modelling from a similar deal....you get the picture
So, the client gets a starting point and it's tweaked from there. Problem is, you inherit everything. There's not a huge amount of "improving' from the last successful deal, just tweaking.
Unless you've got a really sophisticated client, it's just the same shit over and over for the most part. They're guided by their advisors rather than politics.
The concept of a truly bespoke deal is just too expensive and takes too long.
It's the same the world over IME. Most PPP deal teams weakest link is on the client side, the ones calling the shots. That's not supposed to be derogatory to them, it's just impossible for them to know what they doing if they only do it once or twice in their career, compared to those doing it non stop day in day out, it's hard for them to not be guided.