42. Community secondary legislation on public contracts and concessions mainly concerns the phase of award of a contract. Secondary legislation does not cover comprehensively the phase following selection of the private partner. However, and the principle of equality of treatment and the principle of transparency resulting from the Treaty generally rule out any intervention of the public partner after selection of a private partner, in so far as any such intervention might call into question the principle of equality of treatment between economic operators.38
43. The often complex nature of the arrangements in question, the time which may elapse between the selection of the private partner and the signing of the contract, the relatively long duration of the projects and, lastly, the frequent recourse to sub-contracting mechanisms, sometimes complicate the application of these rules and principles. Two aspects are covered below: the contractual framework of the PPP and sub-contracting.
____________________________________________________________________________________________
38. See Case C-87/94, Commission v. Belgique (Bus Wallons), Judgment of 25 April 1994, point 54. See also Case C-243/89, Commission v. Danemark (Bridge on the Storebaelt), Judgment of 22 June 1992.