The 2 ½ hour talks ended in stalemate with the trade unions, SIPTU and NBRU, expecting tomorrow clarification on proposals given by Mr Brennan.
Those proposals include an independent facilitator for intensive discussions in a tight timeframe. If the unions agree to these talks then Mr Brennan will postpone legislation on the breakup and privatisation of CIÉ till the talks have concluded.
Mr Brennan described the meeting as "tough and tense" and said the situation "remains difficult" Mr Tony Tobin, branch secretary SIPTU said there was "a frank exchange of views" at the meeting.
This morning's meeting at the Department of Transport was the fourth between the Minister and the unions, who oppose his plans to privatise as much as 25 per cent of Dublin Bus and to break up CIÉ.
A spokesperson for all the unions at the meeting said: "The Minister and his officials asked for time to consider what the unions had said to him and they hoped to be in a position to respond either later this evening or tomorrow morning.
"In the event that there is the possibility of opening up a new process for discussions the Minister agreed that:
"He listened carefully to what we had to say about his regular media pronouncements and acknowledged he knew little about industrial relations.
"His said that his comments were made in the context of his role as a politician.. He appreciated the difficulties that some of his pronouncements had caused the unions and acknowledged that some of the impasse that had occurred was of his own making.
Previously unhappy with the level of consultation over the Minister's plans, unions have pointed to their mandate for striking unless Mr Brennan agrees to what they see as a genuine process of talks.
They have also insisted that the Minister halts the "practice of handing routes to private operators without telling anyone".