The assignment was written by the co-worker but copied from other students' assignments, the ERA said.
Two specialists investigators were appointed to consider the allegations, one of whom concluded the evidence of copying amounted to a series breach of standards and conduct, the other finding there was no copying or plagiarism "that wasn't within acceptable boundaries".
The Fire Service said statements that the assignment was written by Mr X were dishonest and false and his responses were inconsistent.
"Work emails submitting [the assignment] as his work were dishonest and his completion of the tertiary institution's course was also dishonest in the circumstances," the Fire Service found before dismissing him in July 2017.
Mr X sought reinstatement to his old job until his case could be heard in full but the ERA found that he did not have a strong case based on the evidence submitted so far.
From the affidavits, Mr X appeared to accept he had submitted a document he did not write while blaming the co-worker for giving it to him in a different form to the one they had originally worked on together, the decision said.
The co-worker stated Mr X had instructed her to do the entire assignment for him and he did not write and any part of it.
"Given Mr X's acceptance he submitted [the document] in support of his tertiary qualification, there is a reasonable basis for the respondent [the Fire Service] to be concerned about his honesty," the decision said.
Mr X's case for reinstatement was based on factors including difficulties he would have obtaining alternative employment given his age; the health issues his unemployment was causing him; and financial implications causing him stress and anxiety. It was subsequently accepted Mr X had received $19,846 after his dismissal and there were no financial implications, the ERA said.
However, the ERA found reinstatement would create difficulties for the Fire Service that outweighed the difficulties Mr X would face.
"There are issues about the impact upon Mr X's role if reinstated given his apparent admission of submitting a false document. The misconduct may have repercussions upon his credibility as an expert witness, educator and representative for the respondent."
Other Fire Service employees' interests also needed to be considered, including the co-worker who was unwell and allegedly "scared" of Mr X.
"Several respondent employee witnesses make serious allegations against Mr X. One witness would be his immediate superior," the decision said.
The ERA was also presented with evidence from a third-party employment advocate who allegedly continued to publicise the bullying allegations and had made threats to lay a complaint with police about Mr X's daughter unless the Fire Service changed a report about Mr X.
The ERA took this into account when granting interim name suppression, given the detrimental impact it could have on Mr X's health.