I think nothing is stopping municipalities from getting additional partners to come together on projects. The real question is what role the infrastructure bank will or won't play in that.
If the infrastructure bank forces you into a project with a 10% interest rate instead of providing you with an interest rate of 1%, that will make a huge difference for whoever is finally paying the cost, whether the taxpayer, a ratepayer, a user-fee payer, or a municipal government. There's a huge interest rate differential, particularly on longer-term projects. The longer the project, the more interest rate costs you're incurring.
I would see the role of the federal infrastructure bank as getting the best interest rate deal for municipalities such that they pay the lowest possible rate, as opposed to forcing them into structures where they pay, in essence, the highest possible rate because of the P3 structure.