The classic funding mechanism that matches best with that model is municipal bond issues, where private funders get to tap into the future revenue stream of the

The classic funding mechanism that matches best with that model is municipal bond issues, where private funders get to tap into the future revenue stream of the region as a whole and the local government get cash up front to spend on capital investment. Since the government does capture revenue from those positive externalities (via a more robust tax base) it aligns incentives nicely. Not sure why they seem to have gone out of favor to be replaced with public-private-partnership type arrangements, where the private entity gets just profits from tolls or tickets in exchange for fronting some cash.