The Irish Infrastructure Fund (IIF) has agreed to buy the remaining 22% stake of Enet from US company Granahan McCourt.
The move will give the investment fund complete control of the company.
Granaham McCourt said it had decided to sell its remaining stake so that it could fully commit its time, energy and resources to the National Broadband Plan.
Led by David McCourt, Granaham McCourt is leading the National Broadband Ireland consortium, the only remaining group still bidding to win the Government's National Broadband Plan contract.
Enet is also one of the service providers to the consortium, along with Denis O'Brien's Actavo, KN Group and Nokia.
Limerick-based Enet operates the Metropolitan Area Networks here - networks of state-owned ducting and fibre that link the main commercial and public buildings to private telecom operators.
It also operates wholesale telecoms infrastructure.
The IIF is a state backed fund that is managed by Australian investment managers, AMP Capital, and Irish Life Investment Managers.
The IIF bought a 78% stake in Enet in August of last year from investment company Oak Hill Advisors as well as other investors for €150m.
AMP Capital's Philip Doyle said since then Enet has demonstrated the high quality of its business and its potential for growth.
"Today, Granahan McCourt are pleased to be putting our full and absolute commitment behind the Irish Government's National Broadband Plan," David McCourt said in a statement.
"Granahan McCourt has led the consortium since the Pre-Qualification Questionnaire (PQQ) was submitted in March 2016 and as we are now looking ahead to delivering the NBP and in order to fully commit our time, energy and resources to this ambitious project, we have taken the decision to sell our remaining stake in Enet", he added.
Last week it emerged the Minister for Communications Denis Naughten had met Mr McCourt for dinner during a trip to New York in July.
At the meeting, which came around the time the make up of the consortium was changing, Mr McCourt reaffirmed its commitment to the National Broadband Plan.
Opposition parties have, however, criticised the Minister for meeting Mr McCourt while the tendering process for the National Broadband Plan was still underway.
At the weekend it emerged that Luxembourg based Cube Infrastructure Managers, who failed in its attempt to buy the 78% stake in Enet last year, is suing Granahan McCourt in a US court for allegedly breaching the terms of a letter of intent and non-disclosure agreement around the proposed deal.
Granahan McCourt has denied all the accusations made against it.