Public - private partnerships. Are they systemically desirable?

My experience of PPP's in the Blair years in Britain make me highly suspicious of PPPs. George Monbiot captures many of my concerns. What I am keen to understand is whether they are systemically desirable, or not, and what purpose could legitimately be assigned to them from the perspective of good governance? It is not easy to discern the answers to these questions. My understanding from the British situation was that they were a convenient means to do business with the private sector as well as being a device to keep debt out of the calculations that determine credit ratings for a country or state (i.e., Moodys!).

I am thus interested to see that there is significant dissent with the Victorian Labor Party following a push by the new premier to use PPPs to build new schools as well as the new desalination plant and associated pipeline. It is easy to see this policy shift as 'copy cat' tactics but are those responsible for pushing them the same people as pushed them when Blair was in power? What learning has occurred with whom about their effectiveness in Britain? I hope the growing dissent in Victoria will allow these questions to be explored and thus bring greater transparency to the role of PPPs.