Former taoiseach Mr John Bruton asked that an inquiry be carried out into the 1995 mobile phone licence competition process after Mr Michael Lowry resigned in late 1996, the tribunal was told.
Mr Seán Donlon, a former senior adviser to Mr Bruton during the Rainbow Coalition, said he had carried out the inquiry into "the process through which the decision was made".
The tribunal is currently nearing the end of public hearings into the competition process.
It has spent more than two years conducting the inquiry, both in public and in private.
Mr Donlon told Mr Richard Nesbitt SC, for the former department of transport, energy and communications, that he had looked at the documents in relation to the licence competition.
He also spoke with officials, and noted the names of the civil servants involved.
He said he knew the officials to be civil servants of high quality. He knew some of them very well. One of them had joined the Department of Foreign Affairs on the same day as he had.
He said he went back and told Mr Bruton that "the process was such that it could not have been subverted".
He said it did not surprise him that the civil servants involved had come to the tribunal and given evidence that their work had not been overborne or interfered with in any way, and that it had been carried out independently.
When Mr Nesbitt said Mr Donlon was in the witness box to give evidence in relation to Sir Anthony O'Reilly, Mr Donlon said: "I'm not sure why I'm here to give evidence."
He said he had originally been contacted in relation to matters to do with auctioneer Mr Mark FitzGerald. "How we got to Glandore is not clear to me."
Mr Bruton met Sir Anthony in Glandore, Co Cork, in July 1996. Mr Donlon said Sir Anthony's complaint in relation to the licence competition was that he hadn't won.
"Complaint may be putting it too strongly." Disappointment might be more appropriate. "He knows he didn't have any right to win the competition."
He said Sir Anthony's career had its origins in State companies, and he was very aware of how processes here worked.
Sir Anthony had been associated with Bord Bainne, a State company. It wasn't as if Sir Anthony was "a US tycoon coming into Ireland who doesn't know how it operates".
"He seemed to feel that the Rainbow Coalition was not treating him as well as he would wish to be treated."
The primary issue was the MMDS issue, but there were also other matters, including the mobile phone licence issue.
It was a sense of disappointment in relation to the licence, and it was mentioned in that context.
It was not that "I scored that try back in whatever and I should have got the licence", Mr Donlon said.
He said that when he told the then US ambassador Ms Jean Kennedy Smith that the decision in relation to the mobile phone licence competition would be made by the government, he had meant it would be taken in accordance with "the green book" which set out the rules for government decisions.
He said the Irish system would be quite different to the US one.
He agreed with Mr Nesbitt that the "government decision" in relation to the licence competition took place against a backdrop where there had been an independent assessment of the bids.
