Subcontractors' costs under subcontracts procured for the alliance are only reimbursed to the NOPs when procured according to the Project Proposal's contracting strategy. This document should be incorporated in the PAA and require that the selection of subcontractors for the alliance is competitively tested, and that the procurement process is transparent. The competitive and transparent selection of suppliers and subcontractors is necessary for public infrastructure projects (including alliances) since sole-sourcing is generally not acceptable under government procurement policies. This is discussed in more detail in Chapter 6.