A spokesperson for the Department of Justice said last night, that Michael O'Neill from Patrickswell who got 11 years for manslaughter, with remission is due for release in May 2007.
Jeremiah Sheehy from Rathkeale will be due for release in February 2008.
He received a 12-year term for the manslaughter of Garda McCabe.
The two men given the longest sentences of 14 years each, Pearse McAuley from Strabane and Kevin Walsh, from Patrickswell are not due for release until August 2009.
The sentences on all four date from February, 1999.
Gardaí and the McCabe family have been angered at generous concessions allowed to the four IRA killers since they were transferred to Castlerea prison from Portlaoise.
McAuley's wedding to Sinn Féin councillor Pauline Tully in January 2003 caused public outrage as the couple and their friends held a huge wedding party after their wedding in the parish church in Kilnaleck, Co Cavan.
The Garda Representative Association have condemned the concessions to the prisoners in Castlerea.
"You couldn't say they are serving their sentences behind bars, it's more like a hotel than anything else," said a GRA spokesman.
After the four were moved to Castlerea from Portlaoise in 1999, the then Justice Minister John O'Donoghue wrote to Ann McCabe about the decision to move them.
Minister O'Donoghue, told Ms McCabe in that letter: "My decision, in the case of the group of prisoners who were convicted in connection with your husband's death is not, I can assure you, based on any thinking on my part that they should have some sort of preferential treatment. It is based on consultations and advice tendered to me, from which it is clear that the transfer would be in the interests of better prisons management, at this time."
In that letter of December 1999, Mr O'Donoghue stated his reassurance given at a previous meeting with Ms McCabe that there was "no question" of granting early release to the four IRA men.
He continued in that letter: "I want to reassure you now, formally and in writing, that the government's position, right from the beginning, was that the men concerned are not covered by the terms of the Good Friday Agreement and that their transfer to Castlerea will have no bearing whatsoever on the question of early release. They will serve their time in Castlerea just as they would have in Portlaoise."