BRUSSELS/MILAN, Nov 8 (Reuters) - Italian state lender Cassa Depositi e Prestiti (CDP) and Australian fund Macquarie are set to secure unconditional EU antitrust approval for their acquisition of broadband network company Open Fiber, sources close to the matter said on Monday. State-controlled Enel (ENEI.MI) and CDP currently have joint control of Open Fiber, which had been set up to roll out fibre optic cables to help Italy catch up with the rest of Europe.The deal will increase CDP"s Open Fiber stake by 10% to 60% while Macquarie will acquire 40%. The approval could help a long-mooted plan to merge Open Fiber"s network with that of Telecom Italia (TIM) (TLIT.MI), regaining traction at a time when TIM"s top investor Vivendi is calling into question the role of the group"s CEO Luigi Gubitosi after two profit warnings in the span of a few months. read more CDP is the second-biggest shareholder in TIM, behind French media company Vivendi (VIV.PA), which some analysts had feared could complicate the Open Fiber deal with the EU competition enforcer. The European Commission which is scheduled to decide on the deal by Nov. 10, declined to comment.Enel, Macquarie and CDP also declined to comment. The previous government of Prime Minister Giuseppe Conte had backed the single-network plan, which would avoid duplicating investment in fibre rollout. However, some ministers of the new government led by Mario Draghi have cast doubts over the plan because of regulatory issues, saying that alternative options are also being considered, though speculation about a tie-up has resurfaced recently.