Appearing before the Senate committee, the company's executive general manager of logistics and facilities management, Derek Osborn, was unable to give specific information about how allegations of the sexual assault of a young boy in 2013 were handled. Nor could he say how many serious assaults or incidents of self-harm had occurred on Transfield's watch.
Transfield's director, Angela-Margaret Williams, was similarly flummoxed when asked about the gender breakdown of the 500 staff.
Like Osborn, she replied that she did not "have that information at hand" - a gap in knowledge that the committee chairman, Labor Senator Alex Gallacher, described as "extraordinary".
The committee also heard that staff from Wilson Security, which is contracted by Transfield, are not screened for working with children.
And it was told that staff monitoring asylum-seekers at risk of suicide and self-harm referred to that duty as "whisky watch".
The inquiry - which will report next month - was ordered in March after an independent review by a former Integrity Commissioner, Philip Moss, uncovered several dozen cases of sexual and physical assault of adults and children at the facility, mainly by Nauruan guards.
Among those who made written submissions is Professor David Isaacs, a Sydney paediatrician who worked on the island late last year.
He wrote that detainees' tents, mostly not air-conditioned despite the sweltering heat, were up to 120m from ablution blocks.
"To go to the toilet at night involves crossing dark, open land, often under the gaze of large male guards." Many children and some mothers would wet their beds "rather than run the gauntlet of a night-time toilet visit".
And their fears are not unfounded. One woman "wept uncontrollably for 10 minutes" while confiding to Isaacs that she had been raped by a cleaner - and that two guards subsequently offered her marijuana and extra time in the hot shower in exchange for sex.
Other submissions detailed self-harm by children as young as 5, guards groping teenagers on the pretext of searching them, and the plight of a young boy who self-harmed and talked about suicide after being sexually assaulted three times.
According to the Asylum Seeker Resource Centre, Australia's largest refugee advocacy group, five to six families live cheek-by-jowl in communal tents "full of mice and cockroaches" and with rats "loitering outside". The mould in the tents causes fungal eye and skin infections.
Families have no privacy from one another or from guards, who can enter tents unannounced at any time.
A former magistrate on Nauru, Australian Peter Law, said in his submission that local police had failed to investigate properly the allegations of sexual and physical assault.
Law, who was deported from the island last year, wrote that "the failure ... to bring charges suggests political interference and highlights an unwillingness to bring to public attention the circumstances of refugees in Nauru generally".
He also suggested that Nauru was becoming a "rogue state", with no commitment to the rule of law, no independent judiciary or media, and a record of stifling dissent.
Nauru refugee centre
• The Australian-funded detention centre on Nauru opened in 2001.
• Newly elected Labor Prime Minister Kevin Rudd announced in December 2007 that his country would no longer make use of the centre.
• Julia Gillard's Labor Government reopened the centre in August 2012.
